GF2 Pro lockups on a once-stable system.

I had an ATi Radeon for months in my PC that ran all my games without a hitch. I upgraded to a GeForce2 Pro last night, and it the screen would lockup after 20 min. or so, but the system would still respond (sounds, alt-F4, etc.)

I’ve installed the v32 4-in-1 Drivers from VIA with the the AGP in Normal Mode. I have the latest Leadtek drivers. I printed Leadtek’s suggested BIOS settings and followed them to a T. I have 5 fans in my system and Winfox says my card is “well functioning.”

Any ideas? I haven’t tried the reference drivers yet, but I don’t think that will help much.

FIC AZ11 w/ 750mhz T’Bird
512MB PC133/30GB WD Caviar
GeForce2 Pro/SB Live! X-Gamer

Thanks,
Butch