Windows .jar Can't load new world

[DecentM]

The Windows.jar is there, because I use the .jar Windows launcher, although this problem probably is not associated with it.
Also, this crash happens with unmodified FTB Ultimate pack. I deleted, and launched FTB, but happens all times.

Whenever I try to load a new, or existing world, FTB crashes with this log:
http://pastebin.com/1zM4TXc2
My Computer specs:
http://dl.dropbox.com/u/31273856/DxDiag.txt

It doesn't happen, when I connect to a server, either FTB, or vanilla.

 

[Azgult]

java.lang.IllegalAccessError

This is java being paranoid and not letting mods interact with vanilla minecraft. First things first: update java; this is the sort of thing which easily changed with each version.

 

[DecentM]

Okay, thanks later this day, I will be able to do it.