9:21:50 PM CONSOLE: [SEVERE] java.util.ConcurrentModificationException
9:21:50 PM CONSOLE: [SEVERE] at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819)
9:21:50 PM CONSOLE: [SEVERE] at java.util.ArrayList$Itr.next(ArrayList.java:791)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.EntityTrackerEntry.track(EntityTrackerEntry.java:85)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.EntityTracker.updatePlayers(EntityTracker.java:138)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:589)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
9:21:50 PM CONSOLE: [SEVERE] at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
9:21:50 PM CONSOLE: [SEVERE] Encountered an unexpected exception ConcurrentModificationException