I have the same problem. Same video card, same monitor.
The weird thing is, it had been running on DVI for about two weeks. This is a family computer so i'm not sure if somehow the driver got corrupted ... my wife said that she had a window pop-up during windows start that asked her to install Pivot. It sounds like she did, it was not long after that that DVI stopped working... unfortunately i can't confirm the timeframe.
I have reinstalled the ATI driver a few times with no luck.
From what I have read here it looks like i'll have to replace the video card.... although the fact that it was running on DVI makes me wonder about s/w. Any help would be appreciated.