Really Annoying Server Error HELP!!!

[tweedjt]

so this is an error to my tekkit classic server idk how to fix it but it looks like a incompatable mod thats a chunk loader?

2013-05-01 06:41:57 [sEVERE] java.util.ConcurrentModificationException

2013-05-01 06:41:57 [sEVERE]at java.util.HashMap$HashIterator.nextEntry(Unknown Source)

2013-05-01 06:41:57 [sEVERE]at java.util.HashMap$KeyIterator.next(Unknown Source)

2013-05-01 06:41:57 [sEVERE]at net.minecraft.server.World.a(World.java:2448)

2013-05-01 06:41:57 [sEVERE]at net.minecraft.server.ChunkRegionLoader.a(ChunkRegionLoader.java:219)

2013-05-01 06:41:57 [sEVERE]at net.minecraft.server.ChunkRegionLoader.a(ChunkRegionLoader.java:88)

2013-05-01 06:41:57 [sEVERE]at net.minecraft.server.ChunkProviderServer.saveChunk(ChunkProviderServer.java:171)

2013-05-01 06:41:57 [sEVERE]at net.minecraft.server.ChunkProviderServer.saveChunks(ChunkProviderServer.java:221)

2013-05-01 06:42:00 [sEVERE]at net.minecraft.server.World.save(World.java:263)

2013-05-01 06:42:00 [sEVERE]at org.bukkit.craftbukkit.CraftWorld.save(CraftWorld.java:646)

2013-05-01 06:42:00 [sEVERE]at com.mcserversoft.mcssplugin.MCSSmanager$1.run(MCSSmanager.java:225)

2013-05-01 06:42:00 [sEVERE]at org.bukkit.craftbukkit.scheduler.CraftWorker.run(CraftWorker.java:34)

2013-05-01 06:42:00 [sEVERE]at java.lang.Thread.run(Unknown Source)

Please tell me how to remove it all it does is spam my console constantly...

[Recaran]

I had this problem, removing mystcraft worked for me.

Edit-

Just noticed your running tekkit classic. Sorry dude.