This is exactly the same trouble I've been having with CMBO (first the demo and now the full version) as well as CMBB demo. The whole screen turns to odd whitish crud and locks up.
Athlon 1900+
Gigabyte 7VAX-A motherboard (KT400 chip)
Gainward Ti4200 64Mb
Onboard AC97 sound.
BIOS and sound/video/motherboard drivers are current or almost current (haven't tried 52.16 NVidia yet). 30.82 NVidia drivers didn't help.
Problem occurs with sound on or off and at all resolutions and refresh rates. Nothing is overclocked, no AA, no AF on the video. Fiddling with hardware acceleration doesn't help.
There does seem to be a correlation between the time the PC has been doing 3d graphics and the crashes. However the problem only occurs in CMBO/CMBB and Grand Prix Legends (and only then in D3D mode, OpenGL is fine).
However of all odd things the graphics kludge hasn't reoccurred since 10/25 (I know, only two days) when I updated the LAN driver. Hopefully it's gone...
I'm guessing a PCI latency issue. My BIOS doesn't have a setting for PCI latency. If yours does, try adjusting it?