I searched the forums using the 1st line in the stack trace and found a TON but did not find anything that was any help for me.
I am having a error even after a fresh uninstall, download, and re-install of Minecraft 1.6.4. I have no other mods that I am trying to install. The error comes when I try to make a world not loading the game.
9.4.20.923
http://pastebin.com/LMSVKJ4d
9.4.20.916
http://pastebin.com/LHKTK2gG
I really hope to get a solution for this soon.
EDIT: I got FML working for 1.4.7(universal), 1.5.2, and 1.6.2 (installers) so unless there is a new way to use the installer then it should not be a problem with the way I am installing FML...in fact the game loads just fine the crash is only then I try to make a 1.6.4 map.