Power Supply failure? Please help!

I am running very short and time and will thus attempt to make this brief.

My high end PC will run fine no matter what I do, except for when I play games. The computer freezes 3-10 minutes into gaming. The things is, it very rarely shuts off, just freezes and I can do nothing, CTRL ALT DELETE doesn't even register, so I am forced to use the restart button or force power down. In Event Viewer the event is "Critical" and has "Kernel-Power" for Source, "41" for Event ID, and "(63)" as the Task Category. This is likely only because I have to force power down or use the reset button, correct?

The fact that this only happens when I am running high end games would lead me to believe that the power supply is at fault somehow, but the I think that it seems like the computer would turn off completely. Does that make sense?
It seems odd that it only freezes.

I thought it could also be some drivers, and so I have been trying to troubleshoot by uninstalling, re-installing, or downloading new drivers.

In the past I had similar problems to this, (only fails during games) and was able to solve it by System Restore to before certain AVG and Windows drivers downloaded, and that worked for a while.

Is it likely that the PSU is at fault here, even though it still stays on and will restart immediately after?

Is it likely that drivers (AVG, Windows, Windows Security crap, nVidia) are to blame.

I recently upgraded my CPU Heatsink because I thought this problem was due to high PC temperatures (i7-950 up to 85-90 C) during certain games. Could the CPU be damaged, and only show this during high end games?

I haven't forgot about the GTX 570 and that possibility of failure, I suppose I am hoping for driver problems, as well as the fact that problems like this have occurred in the past and it wasn't due to the GPU.

Please guys, help me out, I am in over my head here, or so it seems!

Thanks for reading all of that, and thanks for any and all help and advice you give me!