I have an AMD rig (cpu and gpu) that outright freaks out and lags hardcore when i physically shut off one monitor. Doesnt matter which monitor or what program (web browser, game, etc..) I am running. I have done all the tech simple stuff like restart, changing ports on the card, reinstalling drivers and clean installing drivers. It just doesnt help. If i turn off one of the two monitors (which i like to do when im watching a movie or something) the second monitor lags like im back in win 95 playin Red Barron over a 33.6kbs modem.