Sounds like video issues hands down. I don't see how anyone could like VIA chipsets as they have gotten a lot of bad press and I've had nothing but problems with them. In my opinion VIA sucks the sweat off a dead man's balls and I'll never have another one in my house again.
nForce works fine with NVidia cards but I'm not sure about ATI. But since I'm an NVidia man I could care less about ATI. I'd say either get a diff card or wait for newer drivers. It certainly seems to be about video drivers. As far as it working for several days it sounds like that might be more related to the SATA than anything. Make sure the SATA is working ok. Try running Word or some other dumb app for several days and see if you notice any stalling (other than the usual Microsoft Word stalls and crashes). I bet you will see some.
