How long have you had it? If it's been less than 60 days you just go through EA to get a replacement. You should also google around for a metal pedal, whether you get a replacement or not, because the thing is flimsy and guaranteed to break again.
Or if you want to go all out you can mod a real bass pedal and never worry about the P.o.S. that comes with the game.
The official Rock Band support forum is really the best place to find the kind of info you want.