I've been stricken with the same problem somewhat. I bought a 2.8 GHz MacBook Pro from the Apple Store online. One of the first things I loaded up was Team Fortress 2 via CodeWeavers CrossOver Games application. The 9400M worked fine, but I wanted to see what the 9600M GT could do. Every attempt, within 5 minutes, my computer would BlSOD on me and I would have to hard reboot.
I called Apple and they sent out a replacement and check my serial number online: my computer was built in December so I was hoping that if it was a hardware problem, hopefully this 2nd computer would have been built recent enough to escape it. But alas, I continued to have the same problem while playing Team Fortress 2.
Coming to the realization that this problem has not yet been fixed (even after 10.5.6 and the SMC update), I tried some other games. I downloaded the Redline demo and attempted to see if I could get that game to BlSOD the system, but it played it fine. I figured that it probably wasn't pushing the GPU hard enough.
So, I borrowed a copy of Enemy Territory: Quake Wars from a friend (the only other game I have for the Mac is World of Warcraft and I don't want to relapse into that game again). It's a fairly recent game and I figured that it may demand enough to BlSOD the 9600M GT GPU. I pushed the graphics details all the way up -- played it three times for about 15 minutes each and the 9600M GT had no problems with it.
Following the lead of others, I downloaded smcFanControl2 and set the fans to 5000 RPM and found that pushing the fans faster does mitigate the 9600M GT BlSOD issue. In fact, I haven't had a BlSOD once while I've been using smcFanControl2.
I'm not sure what the exact problem is and I'm not going to speculate based upon the Inquirer's article. It COULD be a hardware problem, but it is also very possible that it is a software problem -- my
guess is the 9600M GT drivers. I know this happens in Boot Camp/Windows too, but the same software/driver issue
could exist on that side as well. I know one thing, running the fans higher with smcFanControl2 mitigates, if not eliminates the issue.
Regardless, this issue is something Apple, and especially Nvidia, need to deal with quickly. Nvidia may go the way of IBM (PowerPC) and AMD if it doesn't get it's act together. Having to run smcFanControl2 just to play a game is not part of the "just works" mantra.