2013-09-27 16:53:42 [SEVERE] java.util.ConcurrentModificationException
2013-09-27 16:53:42 [SEVERE] 	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
2013-09-27 16:53:42 [SEVERE] 	at java.util.HashMap$KeyIterator.next(Unknown Source)
2013-09-27 16:53:42 [SEVERE] 	at net.minecraft.server.v1_6_R3.EntityTracker.updatePlayers(EntityTracker.java:149)
2013-09-27 16:53:42 [SEVERE] 	at net.minecraft.server.v1_6_R3.MinecraftServer.t(MinecraftServer.java:583)
2013-09-27 16:53:42 [SEVERE] 	at net.minecraft.server.v1_6_R3.DedicatedServer.t(DedicatedServer.java:227)
2013-09-27 16:53:42 [SEVERE] 	at net.minecraft.server.v1_6_R3.MinecraftServer.s(MinecraftServer.java:488)
2013-09-27 16:53:42 [SEVERE] 	at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:421)
2013-09-27 16:53:42 [SEVERE] 	at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)
2013-09-27 16:53:42 [SEVERE] Encountered an unexpected exception ConcurrentModificationException
java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at net.minecraft.server.v1_6_R3.EntityTracker.updatePlayers(EntityTracker.java:149)
	at net.minecraft.server.v1_6_R3.MinecraftServer.t(MinecraftServer.java:583)
	at net.minecraft.server.v1_6_R3.DedicatedServer.t(DedicatedServer.java:227)
	at net.minecraft.server.v1_6_R3.MinecraftServer.s(MinecraftServer.java:488)
	at net.minecraft.server.v1_6_R3.MinecraftServer.run(MinecraftServer.java:421)
	at net.minecraft.server.v1_6_R3.ThreadServerApplication.run(SourceFile:583)