When someone tries to make a PS protection field (dblock), they get a crash if it's a big field. This just started, we've been using PS for a long time. I've attached a WG report and the Minecraft client crash log below.

WG REPORT:

Server Information

Java : Oracle Corporation 1.7.0_07 (http://java.oracle.com/)
Operating system : Windows 7 6.1 (amd64)
Available processors: 8
Free memory : 2635 MB
Max memory : 10044 MB
Total memory : 10044 MB
Server ID : unnamed
Server name : ByteUS.com Survival RPG
Implementation : git-Bukkit-1.3.2-R0.1-5-g14140d6-b2361jnks (MC: 1.3.2)
Player count : 11/40

Plugins

GroupManager : 2.0 (2.9.3) (Phoenix)
Minequery : 1.5
WorldEdit : 5.4.2
LoyaltyPoints : 1.0.9
SpleefUltimate : 2.0.2
TagAPI : 1.5
Vault : 1.2.18-b229
WorldGuard : 5.5.3
StopTalkingAutoBan: 2.1.0
iConomy : 7.0
DisguiseCraft : 3.3
Permissions : 3.1.6
BKCommonLib : 1.2
Lockette : 1.7.4
Votifier : 1.9
MobArena : 0.94.4.80
MoneyDrop : 1.6.2
Essentials : Pre2.9.4.1
Citizens : 1.2.1
EssentialsXMPP : Pre2.9.4.1
EssentialsSpawn : Pre2.9.4.1
EssentialsGeoIP : Pre2.9.4.1
VanishNoPacket : 3.12
ChestShop : 3.42
EssentialsChat : Pre2.9.4.1
PreciousStones : 9.4.0
SimpleClans : 2.3.4

CRASH LOG:
Minecraft has crashed!
----------------------

Minecraft has stopped running because it encountered a problem; Unexpected error
This error has been saved to C:\Users\Spyder\AppData\Roaming.minecraft\crash-reports\crash-2012-09-15_20.17.09-client.txt for your convenience. Please include a copy of this file if you report this crash to anyone.

--- BEGIN ERROR REPORT 12e46976 --------
Generated 9/15/12 8:17 PM

• Minecraft Version: 1.3.2
• Operating System: Windows 7 (amd64) version 6.1
• Java Version: 1.7.0_07, Oracle Corporation
• Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
• Memory: 414956912 bytes (395 MB) / 523239424 bytes (499 MB) up to 954466304 bytes (910 MB)
• JVM Flags: 2 total; -Xms512m -Xmx1024m
• LWJGL: 2.4.2
• OpenGL: GeForce GTX 480/PCIe/SSE2 GL version 4.2.0, NVIDIA Corporation
• Is Modded: Probably not
• Type: Client
• Texture Pack: Default
• Profiler Position: N/A (disabled)
• World MpServer Entities: 73 total; [atg['GluteusMax'/4520619, l='MpServer', x=11372.36, y=65.62, z=11599.15], nj['item.item.ingotGold'/4520657, l='MpServer', x=11390.13, y=84.13, z=11567.81], mx['Iron Golem'/4520656, l='MpServer', x=11385.59, y=70.50, z=11557.13], mx['Iron Golem'/4520650, l='MpServer', x=11334.19, y=64.00, z=11575.66], od['Villager'/4520648, l='MpServer', x=11339.66, y=64.00, z=11574.63], od['Villager'/4520649, l='MpServer', x=11373.31, y=64.00, z=11563.28], nz['Spider'/4520620, l='MpServer', x=11373.50, y=42.00, z=11565.50], nj['item.item.rottenFlesh'/4512856, l='MpServer', x=11391.25, y=84.13, z=11568.19], nj['item.item.enderPearl'/4520703, l='MpServer', x=11348.41, y=64.13, z=11579.78], nj['item.item.ingotGold'/4520704, l='MpServer', x=11347.16, y=64.13, z=11580.53], nz['Spider'/4520645, l='MpServer', x=11351.25, y=68.50, z=11558.78], np['Enderman'/4497493, l='MpServer', x=11380.22, y=64.00, z=11557.47], od['Villager'/4520647, l='MpServer', x=11355.72, y=64.00, z=11574.50], od['Villager'/4472343, l='MpServer', x=11341.09, y=64.00, z=11561.59], od['Villager'/4520646, l='MpServer', x=11342.01, y=64.00, z=11561.41], od['Villager'/4472345, l='MpServer', x=11340.50, y=65.00, z=11562.78], od['Villager'/4472347, l='MpServer', x=11351.69, y=65.00, z=11562.69], mx['Iron Golem'/4472342, l='MpServer', x=11339.66, y=71.00, z=11550.03], mx['Iron Golem'/4472341, l='MpServer', x=11332.34, y=71.00, z=11550.03], od['Villager'/4472350, l='MpServer', x=11328.50, y=64.00, z=11588.28], od['Villager'/4472348, l='MpServer', x=11340.41, y=65.00, z=11566.16], mx['Iron Golem'/4472324, l='MpServer', x=11328.19, y=64.00, z=11559.47], mx['Iron Golem'/4472323, l='MpServer', x=11332.34, y=64.00, z=11576.88], mo['Chicken'/4520667, l='MpServer', x=11411.41, y=66.00, z=11620.63], mp['Cow'/4520678, l='MpServer', x=11429.53, y=79.00, z=11614.50], od['Villager'/4520639, l='MpServer', x=11338.28, y=65.50, z=11597.84], no['Creeper'/4533620, l='MpServer', x=11402.56, y=76.00, z=11553.06], np['Enderman'/4533625, l='MpServer', x=11398.09, y=76.50, z=11555.53], oa['Zombie'/4534828, l='MpServer', x=11375.13, y=55.00, z=11632.50], no['Creeper'/4535920, l='MpServer', x=11377.75, y=42.00, z=11631.09], no['Creeper'/4536979, l='MpServer', x=11420.50, y=42.00, z=11548.50], nx['Skeleton'/4537268, l='MpServer', x=11365.50, y=28.00, z=11601.50], nx['Skeleton'/4537910, l='MpServer', x=11351.50, y=64.00, z=11567.50], no['Creeper'/4539042, l='MpServer', x=11376.50, y=58.00, z=11625.50], no['Creeper'/4539043, l='MpServer', x=11376.41, y=56.00, z=11612.97], nz['Spider'/4539044, l='MpServer', x=11379.69, y=58.23, z=11628.18], oa['Zombie'/4539063, l='MpServer', x=11374.50, y=32.00, z=11632.50], oa['Zombie'/4539426, l='MpServer', x=11357.91, y=15.00, z=11606.47], oa['Zombie'/4539427, l='MpServer', x=11358.69, y=18.00, z=11612.94], oa['Zombie'/4539428, l='MpServer', x=11357.56, y=18.00, z=11611.91], np['Enderman'/4539430, l='MpServer', x=11359.47, y=18.00, z=11619.03], aur['GlitchGoblin'/4540417, l='MpServer', x=11373.72, y=64.00, z=11599.38], oa['Zombie'/4541538, l='MpServer', x=11360.50, y=17.00, z=11606.50], nx['Skeleton'/4541539, l='MpServer', x=11358.50, y=17.00, z=11601.50], nx['Skeleton'/4541540, l='MpServer', x=11358.50, y=17.00, z=11599.50], nx['Skeleton'/4541541, l='MpServer', x=11358.50, y=17.00, z=11602.50], nz['Spider'/4541651, l='MpServer', x=11443.50, y=43.00, z=11572.50], oa['Zombie'/4542321, l='MpServer', x=11304.50, y=34.00, z=11582.50], nz['Spider'/4542829, l='MpServer', x=11300.16, y=33.00, z=11628.13], nz['Spider'/4542830, l='MpServer', x=11301.50, y=35.41, z=11626.50], oa['Zombie'/4544206, l='MpServer', x=11435.50, y=60.00, z=11631.50], oa['Zombie'/4544260, l='MpServer', x=11429.50, y=19.00, z=11534.50], oa['Zombie'/4544792, l='MpServer', x=11381.50, y=41.00, z=11552.03], no['Creeper'/4544207, l='MpServer', x=11430.50, y=60.00, z=11636.50], nz['Spider'/4540694, l='MpServer', x=11368.41, y=55.00, z=11637.34], no['Creeper'/4540698, l='MpServer', x=11367.50, y=55.00, z=11640.50], oa['Zombie'/4529748, l='MpServer', x=11450.50, y=44.00, z=11599.50], mo['Chicken'/4472354, l='MpServer', x=11355.16, y=58.64, z=11647.44], no['Creeper'/4531768, l='MpServer', x=11321.50, y=21.00, z=11644.50], nx['Skeleton'/4525025, l='MpServer', x=11387.50, y=35.00, z=11651.50], no['Creeper'/4544169, l='MpServer', x=11451.50, y=11.00, z=11552.50], mt['Pig'/4472365, l='MpServer', x=11382.25, y=63.00, z=11661.13], oa['Zombie'/4524619, l='MpServer', x=11319.50, y=26.00, z=11661.50], oa['Zombie'/4524621, l='MpServer', x=11318.59, y=26.00, z=11659.00], oa['Zombie'/4542278, l='MpServer', x=11428.50, y=18.00, z=11657.50], no['Creeper'/4542280, l='MpServer', x=11435.50, y=18.00, z=11660.50], nj['item.item.egg'/4529636, l='MpServer', x=11355.13, y=57.13, z=11647.88], no['Creeper'/4544168, l='MpServer', x=11452.50, y=11.00, z=11552.50], nx['Skeleton'/4533466, l='MpServer', x=11342.50, y=33.00, z=11665.50], mo['Chicken'/4472366, l='MpServer', x=11389.53, y=67.00, z=11664.41], no['Creeper'/4542279, l='MpServer', x=11438.31, y=18.00, z=11662.09], mp['Cow'/4520681, l='MpServer', x=11452.81, y=79.00, z=11617.50], nx['Skeleton'/4545397, l='MpServer', x=11362.50, y=13.00, z=11654.50]]
• World MpServer Players: 2 total; [atg['GluteusMax'/4520619, l='MpServer', x=11372.36, y=65.62, z=11599.15], aur['GlitchGoblin'/4540417, l='MpServer', x=11373.72, y=64.00, z=11599.38]]
• World MpServer Chunk Stats: MultiplayerChunkCache: 441
• Forced Entities: 104 total; [no['Creeper'/4540698, l='MpServer', x=11367.50, y=55.00, z=11640.50], oa['Zombie'/4539063, l='MpServer', x=11374.50, y=32.00, z=11632.50], oa['Zombie'/4542321, l='MpServer', x=11304.50, y=34.00, z=11582.50], nj['item.item.ingotGold'/4520633, l='MpServer', x=11324.59, y=64.13, z=11624.41], nz['Spider'/4540694, l='MpServer', x=11368.41, y=55.00, z=11637.34], no['Creeper'/4531768, l='MpServer', x=11321.50, y=21.00, z=11644.50], aur['GlitchGoblin'/4540417, l='MpServer', x=11373.72, y=64.00, z=11599.38], no['Creeper'/4539042, l='MpServer', x=11376.50, y=58.00, z=11625.50], no['Creeper'/4539043, l='MpServer', x=11376.41, y=56.00, z=11612.97], no['Creeper'/4544207, l='MpServer', x=11430.50, y=60.00, z=11636.50], np['Enderman'/4497493, l='MpServer', x=11380.22, y=64.00, z=11557.47], oa['Zombie'/4544206, l='MpServer', x=11435.50, y=60.00, z=11631.50], nz['Spider'/4539044, l='MpServer', x=11379.69, y=58.23, z=11628.18], atg['GluteusMax'/4520619, l='MpServer', x=11372.36, y=65.62, z=11599.15], nj['item.item.egg'/4529636, l='MpServer', x=11355.13, y=57.13, z=11647.88], aur['GlitchGoblin'/4540417, l='MpServer', x=11373.72, y=64.00, z=11599.38], nx['Skeleton'/4541539, l='MpServer', x=11358.50, y=17.00, z=11601.50], nj['item.item.rottenFlesh'/4512856, l='MpServer', x=11391.25, y=84.13, z=11568.19], oa['Zombie'/4541538, l='MpServer', x=11360.50, y=17.00, z=11606.50], nj['item.item.rottenFlesh'/4512856, l='MpServer', x=11391.25, y=84.13, z=11568.19], nj['item.item.rottenFlesh'/4525048, l='MpServer', x=11371.22, y=64.13, z=11556.19], nx['Skeleton'/4541541, l='MpServer', x=11358.50, y=17.00, z=11602.50], oa['Zombie'/4544792, l='MpServer', x=11381.50, y=41.00, z=11552.03], nx['Skeleton'/4541540, l='MpServer', x=11358.50, y=17.00, z=11599.50], nj['item.item.ingotGold'/4520657, l='MpServer', x=11390.13, y=84.13, z=11567.81], no['Creeper'/4542279, l='MpServer', x=11438.31, y=18.00, z=11662.09], oa['Zombie'/4542278, l='MpServer', x=11428.50, y=18.00, z=11657.50], nj['item.item.bone'/4520659, l='MpServer', x=11379.88, y=67.13, z=11633.59], nj['item.item.ingotGold'/4520704, l='MpServer', x=11347.16, y=64.13, z=11580.53], nj['item.item.ingotGold'/4520660, l='MpServer', x=11379.47, y=67.13, z=11634.97], no['Creeper'/4542280, l='MpServer', x=11435.50, y=18.00, z=11660.50], nj['item.item.arrow'/4520658, l='MpServer', x=11379.03, y=67.13, z=11635.47], nj['item.item.enderPearl'/4520703, l='MpServer', x=11348.41, y=64.13, z=11579.78], nj['item.item.ingotGold'/4520704, l='MpServer', x=11347.16, y=64.13, z=11580.53], nx['Skeleton'/4525025, l='MpServer', x=11387.50, y=35.00, z=11651.50], nx['Skeleton'/4533466, l='MpServer', x=11342.50, y=33.00, z=11665.50], no['Creeper'/4536979, l='MpServer', x=11420.50, y=42.00, z=11548.50], no['Creeper'/4535920, l='MpServer', x=11377.75, y=42.00, z=11631.09], nx['Skeleton'/4537268, l='MpServer', x=11365.50, y=28.00, z=11601.50], nj['item.tile.blockDiamond'/4537916, l='MpServer', x=11374.94, y=64.13, z=11552.31], nj['item.tile.blockDiamond'/4528835, l='MpServer', x=11373.22, y=64.13, z=11555.47], nx['Skeleton'/4545397, l='MpServer', x=11362.50, y=13.00, z=11654.50], nj['item.item.egg'/4529636, l='MpServer', x=11355.13, y=57.13, z=11647.88], nj['item.item.ingotGold'/4520676, l='MpServer', x=11432.72, y=71.13, z=11533.25], oa['Zombie'/4534828, l='MpServer', x=11375.13, y=55.00, z=11632.50], nj['item.item.egg'/4529636, l='MpServer', x=11355.13, y=57.13, z=11647.88], no['Creeper'/4544169, l='MpServer', x=11451.50, y=11.00, z=11552.50], no['Creeper'/4544168, l='MpServer', x=11452.50, y=11.00, z=11552.50], nj['item.item.ingotGold'/4520633, l='MpServer', x=11324.63, y=64.13, z=11624.41], nj['item.item.bone'/4508329, l='MpServer', x=11345.59, y=64.13, z=11617.91], mx['Iron Golem'/4472342, l='MpServer', x=11339.66, y=71.00, z=11550.03], od['Villager'/4472343, l='MpServer', x=11341.09, y=64.00, z=11561.59], nj['item.item.ingotGold'/4508330, l='MpServer', x=11345.94, y=64.13, z=11618.88], mx['Iron Golem'/4472341, l='MpServer', x=11332.34, y=71.00, z=11550.03], mo['Chicken'/4520667, l='MpServer', x=11411.41, y=66.00, z=11620.63], od['Villager'/4472350, l='MpServer', x=11328.50, y=64.00, z=11588.28], nj['item.item.ingotGold'/4520676, l='MpServer', x=11432.75, y=71.13, z=11533.25], nj['item.item.rottenFlesh'/4507625, l='MpServer', x=11355.66, y=76.13, z=11589.13], od['Villager'/4472348, l='MpServer', x=11340.41, y=65.00, z=11566.16], od['Villager'/4472347, l='MpServer', x=11351.69, y=65.00, z=11562.69], nj['item.item.ingotGold'/4507626, l='MpServer', x=11353.94, y=75.13, z=11588.63], nj['item.item.ingotGold'/4520657, l='MpServer', x=11390.13, y=84.13, z=11567.81], od['Villager'/4472345, l='MpServer', x=11340.50, y=65.00, z=11562.78], aur['GlitchGoblin'/4522562, l='MpServer', x=11375.69, y=64.02, z=11597.78], mx['Iron Golem'/4520656, l='MpServer', x=11385.59, y=70.50, z=11557.13], nj['item.item.bone'/4520641, l='MpServer', x=11329.13, y=71.13, z=11584.28], nj['item.item.ingotGold'/4520676, l='MpServer', x=11432.75, y=71.13, z=11533.25], mx['Iron Golem'/4472324, l='MpServer', x=11328.19, y=64.00, z=11559.47], mx['Iron Golem'/4520650, l='MpServer', x=11334.19, y=64.00, z=11575.66], mx['Iron Golem'/4472323, l='MpServer', x=11332.34, y=64.00, z=11576.88], oa['Zombie'/4529748, l='MpServer', x=11450.50, y=44.00, z=11599.50], od['Villager'/4520648, l='MpServer', x=11339.66, y=64.00, z=11574.63], od['Villager'/4520649, l='MpServer', x=11373.31, y=64.00, z=11563.28], nj['item.item.ingotGold'/4520633, l='MpServer', x=11324.63, y=64.13, z=11624.41], od['Villager'/4520646, l='MpServer', x=11342.01, y=64.00, z=11561.41], od['Villager'/4520647, l='MpServer', x=11355.72, y=64.00, z=11574.50], nz['Spider'/4541651, l='MpServer', x=11443.50, y=43.00, z=11572.50], nz['Spider'/4520645, l='MpServer', x=11351.25, y=68.50, z=11558.78], nj['item.item.ingotGold'/4520663, l='MpServer', x=11400.03, y=64.13, z=11578.56], nj['item.item.rottenFlesh'/4520662, l='MpServer', x=11400.88, y=64.13, z=11580.19], nj['item.item.arrow'/4520640, l='MpServer', x=11329.38, y=72.13, z=11585.16], nj['item.item.enderPearl'/4520703, l='MpServer', x=11348.41, y=64.13, z=11579.78], nj['item.item.egg'/4531218, l='MpServer', x=11378.88, y=71.13, z=11518.53], nx['Skeleton'/4537910, l='MpServer', x=11351.50, y=64.00, z=11567.50], mp['Cow'/4520681, l='MpServer', x=11452.81, y=79.00, z=11617.50], mo['Chicken'/4472354, l='MpServer', x=11355.16, y=58.64, z=11647.44], mt['Pig'/4472365, l='MpServer', x=11382.25, y=63.00, z=11661.13], mp['Cow'/4520678, l='MpServer', x=11429.53, y=79.00, z=11614.50], mo['Chicken'/4472366, l='MpServer', x=11389.53, y=67.00, z=11664.41], nz['Spider'/4542829, l='MpServer', x=11300.16, y=33.00, z=11628.13], oa['Zombie'/4544260, l='MpServer', x=11429.50, y=19.00, z=11534.50], nz['Spider'/4542830, l='MpServer', x=11301.50, y=35.41, z=11626.50], nj['item.item.egg'/4531218, l='MpServer', x=11378.88, y=71.13, z=11518.53], oa['Zombie'/4524619, l='MpServer', x=11319.50, y=26.00, z=11661.50], no['Creeper'/4533620, l='MpServer', x=11402.56, y=76.00, z=11553.06], oa['Zombie'/4524621, l='MpServer', x=11318.59, y=26.00, z=11659.00], od['Villager'/4520639, l='MpServer', x=11338.28, y=65.50, z=11597.84], nj['item.item.ingotGold'/4520636, l='MpServer', x=11316.91, y=64.13, z=11636.69], np['Enderman'/4533625, l='MpServer', x=11398.09, y=76.50, z=11555.53], np['Enderman'/4539430, l='MpServer', x=11359.47, y=18.00, z=11619.03], oa['Zombie'/4539428, l='MpServer', x=11357.56, y=18.00, z=11611.91], oa['Zombie'/4539427, l='MpServer', x=11358.69, y=18.00, z=11612.94], nz['Spider'/4520620, l='MpServer', x=11373.50, y=42.00, z=11565.50], oa['Zombie'/4539426, l='MpServer', x=11357.91, y=15.00, z=11606.47]]
• Retry Entities: 0 total; []

java.lang.ClassCastException: aga cannot be cast to afe
at axl.a(SourceFile:25)
at axl.a(SourceFile:10)
at axs.a(SourceFile:100)
at axs.a(SourceFile:93)
at avb.a(SourceFile:310)
at auw.a(SourceFile:798)
at auw.b(SourceFile:685)
at net.minecraft.client.Minecraft.J(SourceFile:607)
at net.minecraft.client.Minecraft.run(SourceFile:535)
at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT fba89872 ----------

i also get a crash when using optifine. without optifine it didnt crash

i think its confused by the glass, so i changed it to ice instead, and that didnt seem to crash me

For me this happens using unmodded client on two different PCs and user accounts. I'm wondering if it's because my map is so huge. 11.4GB right now. About to run the server on a different PC and see if that fixes it, but I think it's software related not hardware. Will update once tested this way.

Try changing theglass to ice like I did
Change the instances of blockid 20 to I think 79

There are 2 or 3 of them to change

Weird ive had that same error (java.lang.ClassCastException: aga cannot be cast to afe) for something completely different, while moving chests in PilotCraft. Looks like it may be a minecraft or bukkit bug. Try changing glass to something else. Or revert to an older version of minecraft. Not a PS bug, nothing I can do about it.