java.util.ConcurrentModificationExceptio ??

Anyone ever see this? Causes server to lockup... anyone know what triggers it?

Code:

java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:810)
        at java.util.HashMap$KeyIterator.next(HashMap.java:845)
        at net.minecraft.server.EntityTracker.a(EntityTracker.java:105)
        at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:319)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:232)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:512)
2011-02-20 22:32:38 [SEVERE] Unexpected exception
java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:810)
        at java.util.HashMap$KeyIterator.next(HashMap.java:845)
        at net.minecraft.server.EntityTracker.a(EntityTracker.java:105)
        at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:319)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:232)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:512)

 

Fill this out please.

 

did you manage to start two servers on the same world or other file?
only way i can see doing that would be to start a server, change the port in properties, and then start it again (in the same folder)

this doesn't seem like a very likely scenario though.. so fill out the questions TNT posted.. (copy/paste the questions/answers HERE)

 

edit:
nevermind, this isn't plugin related as I'd originally thought

 

Strangely - http://pastie.org/1624653 is happening only AFTER I installed the multiworld feature.

Happens on cb 440 -> 487
Disabled the portal to the nether - it doesnt happen.