I'm actually glad that people are starting to have this problem...
Let me first make assumptions that everyone with this problem has a Unibody MacBook Pro running the 9600MGT.
Let me also make the assumption that everyone with this problem either ran XP in Bootcamp before, or never ran Windows at all.
Here's the story as I can fully understand it. To let everyone know, this problem has been around for about a year now, and Apple hasn't done jack squat about it. Trust me, it pisses me off to no end.
Basically, there is either a bug in the Nvidia driver, or a problem with the chipset in the Unibody MacBook Pro's. I'm leaning more towards the chipset since it's not widespread for all laptops with the 9600M GT in them.
The driver will reduce the clock rate while in Vista or 7 to save power, and allow the computer to stay cooler. Why waste energy anyway? Well, when it does this, it puts the GPU in an unstable state, meaning that basically anything can disrupt it and cause the computer to freeze. Most people with the issue have noticed this while in Firefox when they try to scroll. Usually this happens when the laptop is in an idle, or near idle state (aka on Firefox, Word, etc...) Anything that is not really taxing the CPU and GPU that much.
Play games? The laptop will last all day long. Read email on Firefox? Yea, it will randomly freeze.
So, there is no real fix for the issue. A member here on MR has found a way to keep this from happening though.
Download Rivatuner and follow
these instructions.
The reason why I'm glad this is happening is so it might get a little more attention. Apple has known about this issue since December I know. I called them nearly every day because I could not use my brand new $2500 (At the time) to program with for one of my classes because it would randomly freeze. I really hope to see more and more people complain about this as they get off the XP wagon and move on with Windows 7.
Also, the reason why XP doesn't have this issue is that the Nvidia driver for XP has a bug that keeps the GPU in High Performance 3D mode.
Read
this thread for more, very useful, information.