I'm suffering from an issue similar to this one. I found that switching to VT and back to X a couple of times seems to fix the problem, but obviously this isn't a real solution. Also because, with KMS, switching to console is not going to do anything to the graphic card (and this is why I'm keeping kms disabled, as the issue is still happening with recent kernel and video drivers).
With respect to the original submitter situation, I think I'm luckier because it doesn't happen always. It happens "sometimes" when switching from VT to X (or starting X), when exiting powersave mode or when I turn on the display with an X session active. Sometime the screen looks ok and all works fine, sometimes I see some pixel flashing or fuzzy images (but never both) and then the monitor will lose the video signal after some second. Sometimes instead images are sharp but if the screen changes too much the signal is lost immediately. I don't think it's exclusively due to the monitor size because I had the same problem with the same card but a smaller display (15" LCD at 1024x768): with the VGA connection it worked fine, the symptoms described above appeared using DVI. But surely the problem is correlated with the size, because it happened about one time every ten with the 15" display, and now it happens approximately one time every three with a 22" display (1680x1050 LCD). ciao, Riccardo
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