Starting with the basics, are you using the most recent reference drivers for your video card? Also, use dxdiag.exe to check for any problems with DirectX. I suspect that most of your applications require DirectX 7.0a, so check into that.
Is this the only video-related issue you're experiencing? Your Thunderbird 800 @ 927 looks like it may be a nonstandard FSB. If that's the case, the video card may hiccup occasionally (actually, any device could cause problems if the PCI/AGP bus is out of spec). If it isn't a huge hassle, try setting it back to default speed and see if the problem persists.
When the video freezes, can you kill it with a three-finger salute or does the machine hard-lock?
Best regards,
Floyd