2013-02-15 10:34:10 [SEVERE] net.minecraft.server.v1_4_R1.ReportedException: Exception ticking world entities
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:575)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:485)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:420)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
2013-02-15 10:34:10 [SEVERE] Caused by: java.util.ConcurrentModificationException
2013-02-15 10:34:10 [SEVERE] 	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
2013-02-15 10:34:10 [SEVERE] 	at java.util.ArrayList$Itr.next(Unknown Source)
2013-02-15 10:34:10 [SEVERE] 	at org.bukkit.craftbukkit.v1_4_R1.Spigot.activateEntities(Spigot.java:126)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.World.tickEntities(World.java:1244)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.WorldServer.tickEntities(WorldServer.java:479)
2013-02-15 10:34:10 [SEVERE] 	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:571)
2013-02-15 10:34:10 [SEVERE] 	... 4 more
2013-02-15 10:34:10 [SEVERE] Encountered an unexpected exception ReportedException
net.minecraft.server.v1_4_R1.ReportedException: Exception ticking world entities
	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:575)
	at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
	at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:485)
	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:420)
	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
Caused by: java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at org.bukkit.craftbukkit.v1_4_R1.Spigot.activateEntities(Spigot.java:126)
	at net.minecraft.server.v1_4_R1.World.tickEntities(World.java:1244)
	at net.minecraft.server.v1_4_R1.WorldServer.tickEntities(WorldServer.java:479)
	at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:571)
	... 4 more