Not waking from sleep

Hi guys,
I recently bought a 15" Macbook Pro. Sometimes after putting the Mbp to sleep I can't get it to wake up. It makes the usual noises but the screen remains black. This only happens every once in a while. There isn't a Apple store nearby so I would probably have to send it in, which I don't really want to do (need it for school) if possible. Any help would be appreciated. Thanks.

The problem seemed to be istat pro. I got the heads up from another forum and after I deleted it, no more wake issues. Just thought I'd post in case anyone else was having the same problem.

omg i was having the exact same issue, in fact I just posted about it.
i just deleted istat pro, hopefully it solves my "wake" problem as well

thank you so much