I got this error message several times today on my Unibody MacBook Pro 15, 2.53 Core 2 Duo, 9400M / 9600M GT, 4 GB DDR3. I was using the 9600M in Photoshop when I got this message: I rebooted like it stated and the computer made a beeping noise for a few seconds, but it wouldn't boot. I waited a while and it booted, then I sent an error message to Apple. The computer ran without problems on the 9400 for a good hour or so, then I got the message again. I plan on taking it to an Apple store sometime this week, but I just wanted some insight as to what might be going wrong. I think that it might be the ram or maybe the gpu but I'm really not that sure. Any help would be appreciated.