Server Crash. Stacktrace included, maybe someone knows the cause?

Hello everyone.

Since awhile I'm getting this rather annoying server crash. Happens randomly and intervals vary greatly. Now does any of you Java wizards may know the cause of it? Any pointer would be most helpful.

Is it caused by a plugin? Corrupted map? (I ran all worlds through chunkster already)
Or maybe something else?

Any help would be much appreciated.