I tried moving down to 1024x768, but no joy. I also applied a BIOS update, but no change. In the list modes screen I have everthing from 640x480, 256 color, 60 hz to 1280x1024, 85hz.
I'm wondering if it's just a funky driver. It could be an oddity with directx 8.1, too, for xp. Ah, well.