I am in the process of checking my video card. I have a MBP mid-2009 version and my computer freezes randomly throughout the day no matter what I am doing. I've tried upgrading my RAM, a new hard drive, and a updated OS (Lion to Maverick). I did each "possible solution" one at a time to see if any one would fix the issue and nothing. I just read a thread that stated they blew the dust off the video card and that fixed the issue.
https://discussions.apple.com/thread/2048529?tstart=0
Let me know if this helps.