Minecraft - Saving Chunks Error

[Fragma]

Did a quick search.
Appears to be mods you have added?
Try this mate.

When you start the game, click "options" There should be a button/check box that says "Force Update" Click it, and then log in. Minecraft will redownload and replace all it's files. Try and start it and see if It crashes now.

And next time be a little more careful on what mods you download.
I find that texture packs can do the same thing as the Xray mod.

I have no idea if it will work as i dont play. But it does appear to be a common problem.

Yeh I saw that but forcing an update didn't do anything. It seems to be a problem with the actual level rather than the minecraft.jar. Thanks anyway.