Posing Model problems

I finaly got it so System would let me open a project i had going a while ago, not sure why it keeped saying I didn’t have permisions >.> But now it’s letting me, so I went back to it.

ANYWAYS, I was working on rigging this lil guy upand I wanted to make this quadraped character stand up on his hinds. However, everyting scrunches so heavily. I’ve been tryin figure out how to fix it, even ajusting weight paintings here and there, but not seeming to get it out… Any sugestion would be nice if yall would please.

I posted the model here for now http://www.pasteall.org/blend/11144