Yep. I had the same problem when I was on AGP. It turned out my mainboard drivers had become partially corrupt-namely the AGP gart driver. If you don't know the model number of your mainboard download belarc and look under "Main Circuit Board". Now, as Fycus said, download and install the latest drivers for your paticular board, but don't forget to uninstall the old drivers first. Also, it won't harm to install the latest ATI drivers, but again, uninstall the old drivers first.