So a friend got Java 8 last night, doesn't seem to be working with this client/game. Not sure if it was deeper than just a version difference but that is what I'll base it off of, due to lack of serious java knowledge. Anywho. If you're getting error code 0, it may be because of Java [version]8. If this is the issue, just roll back to java 7. GG.
It is but some versions do work but some don't as some ignore the perm gen size to start up forge and there probably not going to fix it as it's 1.6.4 and they are probably working on 1.8!
It's no issue with the perm gen. It's just a change in java 8 update 20 which made it incompatible with forge and they will not fix it for 1.6.4, only for 1.7