On the official Apple website, it says,

Includes extensive graphics enhancements.

Max just informed me that there was a page located here that said this firmware update would fix the overheating issues with my Santa Rosa MacBook Pro. How a software update can fix a hardware glitch is beyond me, but did you notice that the page no longer exists? Does this mean that they decided it wasn’t actually a fix?

This is what happened to my laptop. It would do this more often when I had the external display hooked up and when I was running lots of programs (the laptop was hot). Usually I was using A/C power. This would be resolved after a forced reboot, but would keep happening until one day the display just wouldn’t turn on.