I have seen a problem very like this, on multiple (non-apple) systems with Nvidia display adapters.
In all cases, the problem was software generated (but hardware failure). I first saw it with products from Turbine (Dungeons and Dragons Online, then later in Lord of the Rings Online), but then started seeing it with Blizzard's ten ton gorilla World of Warcraft as well.
In the Turbine products, the fix was VERY simple. In advanced graphics settings, there was an option 'Sync to refresh rate'. With it unchecked, in less than a half hour I would have the entire system lock up hard, with an audio loop or a loud screech, and initially totally corrupted display that went to black when the monitor put itself to sleep. With it checked, I could run for 24 hours straight (tested) without an issue.
In World of Warcraft, I had the issue when running full screen. Again, a looped audio or piercing screech, hard locked system, display artifacts followed by the display shutting down/going to sleep (for black screen). In this case, I found no software settings that seemed to affect it directly. By running in Windowed mode (not fullscreen) it stopped happening.
Some time after that, One of Blizzard's patches (or one of Nvidia's) seems to have corrected the issue. Currently, I can run fullscreen with the same video card and not have the screech and halt come up.
I have NOT seen this come up on my MacbookPro 17" yet, but I only play Warcraft in OSX mode, not boot camp, and I play it windowed there anyway.
YMMV, but I wanted to post this. When I helped Turbine troubleshoot it, they actually put an entry in their FAQ for me. 🙂
THe 'hardware failure' seemed to be related to the video being overdriven by software settings, until it thermally locked up (or locked up in a way consistent with thermal overload). Powercycling the computer would temporarily solve it, but unless there was some time between restart and running the offending game, your time-to-lockup-screech would drop reboot to reboot until it would fail the instant you ran the game/logged into the game world.
--
Paul