Video problems waking from sleep

I have two computers running Vista Ultimate that have exhibited a problem when waking from standby. After logging on, the screen goes black and stays black, or you get a colored screen (bluish green) and diagonal lines moving around. In one case (Nvidia) I got this problem after installing a newer driver. Doing a driver rollback fixed it. In the other case, a laptop with a ATI 1150 card, doing a driver update fixed the problem.