Sorry I don't have much more info than that but here is a crash log

---- Minecraft Crash Report ----

WARNING: coremods are present:
CCLCorePlugin (CodeChickenLib-1.8-1.1.2.115-universal.jar)
FMLPlugin (InventoryTweaks-1.59-176.jar)
CCCDeobfPlugin (unknown)
CodeChickenCorePlugin (CodeChickenCore-1.8-1.0.5.34-universal.jar)
NEICorePlugin (NotEnoughItems-1.8-1.0.5.82-universal.jar)
Contact their authors BEFORE contacting forge

// I blame Dinnerbone.

Time: 5/3/15 3:39 PM
Description: Updating screen events

java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
at java.util.ArrayList$Itr.next(ArrayList.java:851)
at net.blay09.mods.eirairc.client.gui.base.tab.GuiTabContainer.mouseClick(GuiTabContainer.java:77)
at net.blay09.mods.eirairc.client.gui.EiraGuiScreen.func_73864_a(EiraGuiScreen.java:124)
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:544)
at net.blay09.mods.eirairc.client.gui.EiraGuiScreen.func_146274_d(EiraGuiScreen.java:103)
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:516)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1662)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1021)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:345)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

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

-- Head --
Stacktrace:
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
at java.util.ArrayList$Itr.next(ArrayList.java:851)
at net.blay09.mods.eirairc.client.gui.base.tab.GuiTabContainer.mouseClick(GuiTabContainer.java:77)
at net.blay09.mods.eirairc.client.gui.EiraGuiScreen.func_73864_a(EiraGuiScreen.java:124)
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:544)
at net.blay09.mods.eirairc.client.gui.EiraGuiScreen.func_146274_d(EiraGuiScreen.java:103)
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:516)

-- Affected screen --
Details:
Screen name: net.blay09.mods.eirairc.client.gui.servers.GuiServerConfigContainer

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityPlayerSP['columna1'/5704086, l='MpServer', x=397.43, y=5.00, z=-130.24]]
Chunk stats: MultiplayerChunkCache: 441, 441
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: 19.00,64.00,165.00 - World: (19,64,165), Chunk: (at 3,4,5 in 1,10; contains blocks 16,0,160 to 31,255,175), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 1112413999 game time, 1117647999 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Forced entities: 40 total; [EntityHorse['Donkey'/5649367, l='MpServer', x=444.13, y=71.00, z=-118.31], EntityWitch['Witch'/5704147, l='MpServer', x=433.50, y=37.00, z=-159.50], EntitySkeleton['Skeleton'/5704145, l='MpServer', x=435.50, y=27.00, z=-158.50], EntityBat['Bat'/5704144, l='MpServer', x=443.13, y=17.10, z=-159.50], EntityCreeper['Creeper'/5704159, l='MpServer', x=439.31, y=24.00, z=-166.50], EntitySkeleton['Skeleton'/5704158, l='MpServer', x=440.50, y=30.00, z=-166.50], EntityArmorStand['Armor Stand'/5649375, l='MpServer', x=459.50, y=70.00, z=-143.50], EntityEnderman['Enderman'/5704157, l='MpServer', x=440.50, y=30.00, z=-165.50], EntityZombie['Zombie'/5704156, l='MpServer', x=442.50, y=26.00, z=-167.50], EntityArmorStand['Armor Stand'/5649373, l='MpServer', x=458.50, y=70.00, z=-143.50], EntityBat['Bat'/5704795, l='MpServer', x=425.09, y=20.09, z=-102.59], EntityZombie['Zombie'/5704153, l='MpServer', x=430.50, y=28.00, z=-177.50], EntityCreeper['Creeper'/5704152, l='MpServer', x=423.50, y=30.00, z=-177.50], EntitySkeleton['Skeleton'/5704135, l='MpServer', x=424.50, y=27.00, z=-157.50], EntitySkeleton['Skeleton'/5704134, l='MpServer', x=429.50, y=27.00, z=-158.50], EntitySquid['Squid'/5704270, l='MpServer', x=347.28, y=46.84, z=-96.72], EntityChicken['Chicken'/5704142, l='MpServer', x=445.16, y=75.00, z=-134.50], EntityBat['Bat'/5705294, l='MpServer', x=432.50, y=27.22, z=-161.84], EntitySkeleton['Skeleton'/5704141, l='MpServer', x=444.50, y=25.00, z=-139.50], EntityCreeper['Creeper'/5704139, l='MpServer', x=418.50, y=22.00, z=-102.50], EntitySkeleton['Skeleton'/5704138, l='MpServer', x=427.59, y=39.00, z=-168.91], EntityZombie['Zombie'/5704137, l='MpServer', x=363.50, y=5.00, z=-106.50], EntityCreeper['Creeper'/5704136, l='MpServer', x=425.59, y=28.00, z=-153.00], EntityCreeper['Creeper'/5704191, l='MpServer', x=444.50, y=30.00, z=-86.50], EntityChicken['Chicken'/5704189, l='MpServer', x=443.94, y=71.50, z=-176.50], EntitySquid['Squid'/5705341, l='MpServer', x=425.69, y=58.56, z=-99.28], EntityCreeper['Creeper'/5704165, l='MpServer', x=438.50, y=6.00, z=-105.50], EntityCreeper['Creeper'/5704164, l='MpServer', x=432.50, y=37.00, z=-160.50], EntitySkeleton['Skeleton'/5704163, l='MpServer', x=440.47, y=25.00, z=-167.97], EntityArmorStand['Armor Stand'/5649376, l='MpServer', x=457.50, y=70.00, z=-143.50], EntityXPOrb['Experience Orb'/5704087, l='MpServer', x=393.47, y=5.00, z=-150.00], EntityCreeper['Creeper'/5704091, l='MpServer', x=412.50, y=47.00, z=-171.50], EntitySkeleton['Skeleton'/5704090, l='MpServer', x=427.16, y=20.00, z=-135.50], EntitySkeleton['Skeleton'/5704089, l='MpServer', x=424.47, y=12.00, z=-142.16], EntityZombie['lil' bby'/5704088, l='MpServer', x=378.13, y=36.00, z=-156.59], EntityCreeper['Creeper'/5705860, l='MpServer', x=444.50, y=28.00, z=-156.50], EntityCreeper['Creeper'/5705867, l='MpServer', x=406.00, y=23.00, z=-104.28], EntityBat['Bat'/5705150, l='MpServer', x=431.19, y=27.03, z=-155.69], EntityPlayerSP['columna1'/5704086, l='MpServer', x=397.43, y=5.00, z=-130.24], EntitySquid['Squid'/5705120, l='MpServer', x=426.16, y=61.91, z=-98.75]]
Retry entities: 0 total; []
Server brand: Spigot
Server type: Non-integrated multiplayer server
Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:407)
at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2488)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:367)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.8
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 128804104 bytes (122 MB) / 554696704 bytes (529 MB) up to 954728448 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
FML: MCP v9.10 FML v8.0.76.1392 Minecraft Forge 11.14.1.1392 Optifine OptiFine_1.8_HD_U_D3 7 mods loaded, 7 mods active
mcp{9.05} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
FML{8.0.76.1392} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Forge{11.14.1.1392} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
CodeChickenCore{1.0.5.34} CodeChicken Core Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
NotEnoughItems{1.0.5.82} Not Enough Items Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
eirairc{3.8.84} EiraIRC Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
inventorytweaks{1.59-176-9318a76-dirty} Inventory Tweaks Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Loaded coremods (and transformers):
CCLCorePlugin (CodeChickenLib-1.8-1.1.2.115-universal.jar)
codechicken.lib.asm.ClassHeirachyManager
codechicken.lib.asm.RenderHookTransformer
FMLPlugin (InventoryTweaks-1.59-176.jar)
invtweaks.forge.asm.ContainerTransformer
CCCDeobfPlugin (unknown)

CodeChickenCorePlugin (CodeChickenCore-1.8-1.0.5.34-universal.jar)
codechicken.core.asm.InterfaceDependancyTransformer
codechicken.core.asm.TweakTransformer
codechicken.core.asm.DelegatedTransformer
codechicken.core.asm.DefaultImplementationTransformer
NEICorePlugin (NotEnoughItems-1.8-1.0.5.82-universal.jar)
codechicken.nei.asm.NEITransformer
Launched Version: 1.8
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics GL version 2.1.0 - Build 8.15.10.2900, Intel
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because ARB_framebuffer_object is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)