I think you got a bad Radeon card. I had a similiar problem to yours especially in relation to the distorted screen and weird colours. I managed to switch the card with a new one, however that made things worse with the corruption spreading onto Windows. I ended up trading it in for a 9100.
I've read on the Dell forums of people with that problem too. Seems like they had better luck than I, as when they exchanged their card, their problems went away with it too.