ConcurrentModificationException When generating new chunks

[mrsal511]

The server has been running fine for several weeks now. Yesterday one of our players was generating new chunks when the server went down with the following error log. This is the first time our server has crashed, let alone error'd to crash. As well, we cannot restart the server as it repeatedly crashes with the same error. Any assistance would be great

 

Error log:

http://pastebin.com/7BVRGn8x

 

Sorry if I posted in the wrong section

[larsgerrits]

One of your mods is adding entities to the world from the wrong thread. It is very hard to track down the mod that caused the error, so the best you can do is remove mods until the error stops.