OK, I updated my BIOS but the lockups didn't stop. To add insult to injury my Quake 3 framerates droppped! Needless to say my good ol' BIOS is back in action.
I'm pretty much definitely going to return to the card but I've made a few interesting observations about it:
Firstly, GLQuake and Quake 2 don't crash at all. I've run multiple timedemos multiple times for several minutes and I played several levels for several minutes, and everything seemed OK. That leaves Unreal/Return To Na Pali and Quake 3 as the problem games. If it was a motherboard problem all 3D games would crash, no?
Secondly, regarding the stuck resolution/refresh in 2D mode, I've discovered that if you install monitor drivers that don't tell Windows what the maximum refresh is, the resolution switching starts to work correctly. For example, instead of installing the 1024 x 768 x 75 Hz monitor driver (where nothing works), instead install the 1024 x 768 driver, which does not specify what the maximum refresh rate is.
The resolution switching then starts to work correctly. The refresh is still stuck at 60 Hz but you can use any tweaking utility to bump up the refresh, given it isn't locked to any specific number. From this observation I can only conclude that nVidia's drivers are incorrectly reading the monitor information provided by Windows. Othwerwise they would work flawlessly like my Voodoo 3 drivers did.
Thirdly, it's pretty much beyond a doubt that power issues are not causing the problems. Given that both the Voodoo 3 and my Celeron 500 burned more power than my P3 650E and my GF2 MX, coupled to the fact that I have jumpered my motherboard to provide extra voltage to the AGP slot (which is enough to power a GF DDR, according to the manual), I'm convinced the issue isn't power-related. I suspect nVidia's drivers more than I suspect motherboard compatibilities.
Oh well, I guess I now have to clean up my system now from all nVidia related items. :frown: