2013-02-07 22:06:24 [SEVERE] net.minecraft.server.v1_4_R1.ReportedException: Exception ticking world
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:563)
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:481)
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:416)
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
2013-02-07 22:06:24 [SEVERE] Caused by: java.util.ConcurrentModificationException
2013-02-07 22:06:24 [SEVERE] 	at org.bukkit.craftbukkit.v1_4_R1.util.LongObjectHashMap$ValueIterator.next(LongObjectHashMap.java:304)
2013-02-07 22:06:24 [SEVERE] 	at org.bukkit.craftbukkit.v1_4_R1.CraftWorld.processChunkGC(CraftWorld.java:1344)
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.WorldServer.doTick(WorldServer.java:166)
2013-02-07 22:06:24 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:559)
2013-02-07 22:06:24 [SEVERE] 	... 4 more
2013-02-07 22:06:24 [SEVERE] Encountered an unexpected exception ReportedException
net.minecraft.server.v1_4_R1.ReportedException: Exception ticking world
	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:563)
	at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
	at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:481)
	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:416)
	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
Caused by: java.util.ConcurrentModificationException
	at org.bukkit.craftbukkit.v1_4_R1.util.LongObjectHashMap$ValueIterator.next(LongObjectHashMap.java:304)
	at org.bukkit.craftbukkit.v1_4_R1.CraftWorld.processChunkGC(CraftWorld.java:1344)
	at net.minecraft.server.v1_4_R1.WorldServer.doTick(WorldServer.java:166)
	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:559)
	... 4 more