The problems probably not with cm, but with the rom itself. Fortunately, you can get to recovery which makes fixing the situation a whole lot simpler. I know you're rooted, but not if you installed a rom. If you did flash a rom, I would make sure it's appropriate to the phone and try flashing it again. If you still want to go back to stock, I'm sure there's a thread over at XDA with specific instructions to do just that.