The 360 controllers always have something wrong them. My two shut off occasionally if you hold them roughly, and if a battery is on 2/4, it'll just shut off until you swap the battery pack with the OTHER controller:-/
Eventually, every controller gets fucked up in some way, lol. That thing where it shuts off at 2/4 battery has happened to WAY too many of my 360 controllers. >_>
I've heard that if you duct tape the backs, it won't happen often, but who has time for that? ~_~ I might just get some plug in ones, but my couch is kind of far from the entertainment center...