Direwolf20 Pack crash then world deleted

[Hirix]

Was playing with the Direwolf 20 pack 1.0.14. After attacking a creeper with a stone cleaver, my game crashed with this crash log:

Spoiler

---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 2/8/14 3:37 PM
Description: Exception in server tick loop

java.util.ConcurrentModificationException
at java.util.WeakHashMap$HashIterator.nextEntry(Unknown Source)
at java.util.WeakHashMap$EntryIterator.next(Unknown Source)
at java.util.WeakHashMap$EntryIterator.next(Unknown Source)
at hats.common.core.TickHandlerServer.serverTick(TickHandlerServer.java:127)
at hats.common.core.TickHandlerServer.tickEnd(TickHandlerServer.java:56)
at cpw.mods.fml.common.SingleIntervalHandler.tickEnd(SingleIntervalHandler.java:34)
at cpw.mods.fml.common.FMLCommonHandler.tickEnd(FMLCommonHandler.java:141)
at cpw.mods.fml.common.FMLCommonHandler.onPostServerTick(FMLCommonHandler.java:274)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:622)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

When I reloaded the game back, I found my world gone, not loading in the singleplayer worlds, yet the folder for the world is all still there.

 

[lavarthan]

Welcome. Not sure about the cause, but a temporary(?) fix is to follow this.

 

[MrCervelo]

I've been getting this crash a lot lately, I ended up removing Hats and Hatstand from the modpack. I've only been like that for about 1-2 hours, but I haven't crashed since.

It was almost getting unplayable for me.