Transient garbage on dual link DVI display
My system shows varying amount of strange artifacts on the display. These artifacts are composed of single horizontal line of invalid primary color component (increased intensity of red, green or blue) and can be typically 1 to 200 pixels long. It might be that every other pixel is affected (in DVI dual link fashion), but as effects are displayed only for one frame, it's impossible to say. Usually artifacts don't begin and end suddenly, but have characteristic property of fading in and out, measured by density of affected pixels.
When using X, these effects occur most typically when there's considerable graphics activity (full screen video playback with mplayer is a good candidate) and obviously are more visible when there are large dark areas. Usually the artifacts are dominated by one of the primary color components, so that, for instance, seeing both red and green artifacts is a rarity. Sometimes after system boot lots of these artifacts appear in text mode before system has loaded the OS.
My guess would be that DVI link TMDS clock and (individual) color component data signal have some sort of jitter problems. I've tried several cables, couple of the latest driver versions, and varying plenty of X server and nvidia settings options without success. One unfortunate option is that my display has a sub-standard TMDS receiver, but the fact that these issues occur more frequently when there's graphics activity on the host, I'd say that can't be the only reason.