Whenever a cart carrying a player goes near a boarding rail sitting on top of an Item Unloader block, the server crashes with the crash report below. There's a Buildcraft wooden pipe and three redstone engines pumping the items out of the Item Unloader. Is it trying to pipe the player into the Loader?

If I restart the server, other players can log in, no problems. However, the player that caused the crash cannot log in again or the server immediately crashes again. It looks real dark, too... like the player is inside the Loader... haha.

Can demonstrate if needed.

-Oneprince

---- Minecraft Crash Report ----
// I blame Dinnerbone.

Time: 5/2/13 9:17 PM
Description: Ticking tile entity

java.lang.NullPointerException
at mods.railcraft.common.util.inventory.manipulators.InventoryManipulator$1.hasNext(InventoryManipulator.java:48)
at mods.railcraft.common.util.inventory.manipulators.InventoryManipulator.tryRemoveStack(InventoryManipulator.java:139)
at mods.railcraft.common.util.inventory.InvTools.moveOneItem(InvTools.java:456)
at mods.railcraft.common.util.inventory.InvTools.moveOneItem(InvTools.java:443)
at mods.railcraft.common.util.inventory.InvTools.moveOneItem(InvTools.java:496)
at mods.railcraft.common.blocks.machine.gamma.TileItemUnloader.emptyCart(TileItemUnloader.java:144)
at mods.railcraft.common.blocks.machine.gamma.TileItemUnloader.func_70316_g(TileItemUnloader.java:60)
at net.minecraft.world.World.func_72939_s(World.java:2196)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:546)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:651)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:274)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:570)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:468)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at mods.railcraft.common.util.inventory.manipulators.InventoryManipulator$1.hasNext(InventoryManipulator.java:48)
at mods.railcraft.common.util.inventory.manipulators.InventoryManipulator.tryRemoveStack(InventoryManipulator.java:139)
at mods.railcraft.common.util.inventory.InvTools.moveOneItem(InvTools.java:456)
at mods.railcraft.common.util.inventory.InvTools.moveOneItem(InvTools.java:443)
at mods.railcraft.common.util.inventory.InvTools.moveOneItem(InvTools.java:496)
at mods.railcraft.common.blocks.machine.gamma.TileItemUnloader.emptyCart(TileItemUnloader.java:144)
at mods.railcraft.common.blocks.machine.gamma.TileItemUnloader.func_70316_g(TileItemUnloader.java:60)

-- Tile entity being ticked --
Details:
Name: RCUnloaderTile // mods.railcraft.common.blocks.machine.gamma.TileItemUnloader
Block type: ID #453 (tile.railcraft.machine.gamma // mods.railcraft.common.blocks.machine.BlockMachine)
Block data value: 1 / 0x1 / 0b0001
Block location: World: (39,63,32), Chunk: (at 7,3,0 in 2,2; contains blocks 32,0,32 to 47,255,47), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Actual block type: ID #453 (tile.railcraft.machine.gamma // mods.railcraft.common.blocks.machine.BlockMachine)
Actual block data value: 1 / 0x1 / 0b0001
Stacktrace:
at net.minecraft.world.World.func_72939_s(World.java:2196)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:546)

-- Affected level --
Details:
Level name: Train World
All players: 1 total; [EntityPlayerMP['test'/281, l='Train World', x=40.28, y=63.42, z=32.50]]
Chunk stats: ServerChunkCache: 616 Drop: 0
Level seed: -4321027402940097324
Level generator: ID 02 - largeBiomes, ver 0. Features enabled: true
Level generator options:
Level spawn location: World: (0,64,0), Chunk: (at 0,4,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 265713736 game time, 274331206 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 35167 (now: false), thunder time: 144285 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: true. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:651)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:274)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:570)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:468)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)

-- System Details --
Details:
Minecraft Version: 1.5.1
Operating System: Windows Server 2012 (amd64) version 6.2
Java Version: 1.7.0_09, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 2012576984 bytes (1919 MB) / 2147024896 bytes (2047 MB) up to 2147024896 bytes (2047 MB)
JVM Flags: 2 total; -Xmx2048M -Xms2048M
AABB Pool Size: 4909 (274904 bytes; 0 MB) allocated, 4251 (238056 bytes; 0 MB) used
Suspicious classes: FML and Forge are installed
IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 71
FML: MCP v7.44 FML v5.1.43.676 Minecraft Forge 7.7.1.676 23 mods loaded, 23 mods active
mcp{7.44} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{5.1.43.676} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{7.7.1.676} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Core{3.5.0} BuildCraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Builders{3.5.0} BC Builders Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Energy{3.5.0} BC Energy Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Factory{3.5.0} BC Factory Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Transport{3.5.0} BC Transport Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Silicon{3.5.0} BC Silicon Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ComputerCraft{1.52} ComputerCraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
CCTurtle{1.52} ComputerCraft Turtles Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
CustomSpawner{1.12.5} [DrZhark's CustomSpawner](CustomMobSpawner 1.12.5.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
DimensionalDoors{1.5.1R1.3.4RC3} Dimensional Doors Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MoCreatures{5.1.5} [DrZhark's Mo'Creatures Mod](DrZharks MoCreatures Mod v5.1.5.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ExtrabiomesXL{3.13.0} ExtrabiomesXL Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
factorization{0.7.27} Factorization Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
factorization.misc{0.7.27} Factorization Miscellaneous Nonsense Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
factorization.dimensionalSlice{0.7.27} Factorization Dimensional Slices Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forestry{2.2.0.0} Forestry for Minecraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MiscPeripherals{3.2} MiscPeripherals Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
mod_TreeFeller{2.2} TreeFeller Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
OCS{0.1.5} OpenCCSensors Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Railcraft{7.0.0.0} Railcraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Profiler Position: N/A (disabled)
Vec3 Pool Size: 3342 (187152 bytes; 0 MB) allocated, 2765 (154840 bytes; 0 MB) used
Player Count: 1 / 20; [EntityPlayerMP['test'/281, l='Train World', x=40.28, y=63.42, z=32.50]]
Is Modded: Definitely; Server brand changed to 'fml,forge'
Type: Dedicated Server (map_server.txt)

For any help it may be, here's a screenshot of the offending site.

Thanks will be fixed, it was crashing because the cart doesn't implement IInventory. And it only crashed when being ridden because ridden carts don't pass a vel == 0 check that they would unridden.

Thanks CJ. Glad I could help.