Internal Server Errors - Kicking me and users randomly

Also not letting us log in sometimes.

I can post the error if someone wants to attempt to analyze it, but it seemed pretty vague. Build 617, lots of plugins.

Anyone else get this?

Over at the server, so here it is:

Code:

02:16:10 [WARNING] Failed to handle packet: java.lang.IllegalStateException: Entity is already tracked!
java.lang.IllegalStateException: Entity is already tracked!
    at net.minecraft.server.EntityTracker.a(EntityTracker.java:72)
    at net.minecraft.server.EntityTracker.a(EntityTracker.java:62)
    at net.minecraft.server.EntityTracker.a(EntityTracker.java:51)
    at net.minecraft.server.WorldManager.a(WorldManager.java:17)
    at net.minecraft.server.World.b(World.java:750)
    at net.minecraft.server.WorldServer.b(WorldServer.java:94)
    at net.minecraft.server.World.a(World.java:1590)
    at net.minecraft.server.Chunk.d(Chunk.java:470)
    at net.minecraft.server.ChunkProviderServer.c(ChunkProviderServer.java:75)
    at net.minecraft.server.PlayerInstance.<init>(PlayerInstance.java:33)
    at net.minecraft.server.PlayerManager.a(PlayerManager.java:37)
    at net.minecraft.server.PlayerManager.a(PlayerManager.java:76)
    at net.minecraft.server.ServerConfigurationManager.a(ServerConfigurationManager.java:106)
    at net.minecraft.server.NetLoginHandler.b(NetLoginHandler.java:87)
    at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:27)
    at net.minecraft.server.NetworkListenThread.a(SourceFile:87)
    at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:368)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:283)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:375)

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

If you didn't figure it out by now.... NaturalGiants was causing the "Entity already tracked" error on mine. Just remove it for now if you have it.