What causes this error?

How can it be fixed?

 

2012-12-11 15:53:15 [iNFO] [sTDERR] t: Exception ticking world entities
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:679)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at ho.r(DedicatedServer.java:252)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:592)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:499)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at fy.run(SourceFile:856)
2012-12-11 15:53:15 [iNFO] [sTDERR] Caused by: java.util.ConcurrentModificationException
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at java.util.AbstractList$Itr.next(Unknown Source)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at java.util.AbstractCollection.removeAll(Unknown Source)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at xv.h(World.java:2023)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at in.h(WorldServer.java:473)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:673)
2012-12-11 15:53:15 [iNFO] [sTDERR] 	... 4 more
2012-12-11 15:53:15 [sEVERE] [Minecraft] Encountered an unexpected exception t
t: Exception ticking world entities
at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:679)
at ho.r(DedicatedServer.java:252)
at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:592)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:499)
at fy.run(SourceFile:856)
Caused by: java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.next(Unknown Source)
at java.util.AbstractCollection.removeAll(Unknown Source)
at xv.h(World.java:2023)
at in.h(WorldServer.java:473)
at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:673)
... 4 more
2012-12-11 15:53:15 [sEVERE] [Minecraft] This crash report has been saved to: L:\modded server\.\crash-reports\crash-2012-12-11_15.53.15-server.txt

 

Any help is appreciated.

What causes this error?

How can it be fixed?

 

Do you even know what you are doing?

 

What are you actually trying to do?

I am not developing, just using some mods.

I have loaded a lot mods and it occasionally sends this error and crashes the server.

I think it is the Mo' Creatures mod that is causing the error but I don't know.

Any help?

What mods? I know that Mo' Creatures and TFC don't work well together.