Can the grey screen of death indicate a graphics card problem?

I have a Mac Book Pro from mid 2009 running moutain lion, but for the past week I have been having sporadic issues where it has been getting stuck on the grey screen of death during a reboot. Lately it has been freezing up, giving me the spinning wheel of death, forcing me to shut it down manually. Then when I try to start it up, it's stuck on the grey screen. I just assumed this would be an issue with the hard drive, and ran through several trouble shooting steps. I opened up disk utility and attempted to repair the drive. After no success, I erased it and reinstalled everything from a time machine back up. That was successful. However, the issue is still occurring. I went to the apple store last week and was told there was no evidence that anything was wrong with my hard drive. Is it possible that there is an issue with my graphics card? Thank you, Please advise.