I have a pc with an nvidia 8600gts which has one HDMI connector and one DVI connector. I have had a dual screen setup working perfectly since at least 9.04 but due to a harddrive crash I did a fresh install (as opposed to my regular "upgrade" routine) of 12.04.

My main screen (dvi) is setup to use 1920x1200 while my second screen is set up to use 1920x1080. The second screen behaves "odd" to say the least. When I first turned it on, it went black half the time, then finally it "stabilized" into a fuzzy desktop. By fuzzy I mean the text looks mangled etc, it looks as if the resolution is wrong. On top of that the second screen popped up a warning that it was not running in its optimal resolution (being 1920x1080). And yet xrandr had this output:

Screen 0: minimum 320 x 200, current 3840 x 1200, maximum 8192 x 8192
DVI-I-1 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
1920x1200 60.0*+
1920x1080 50.0 60.0
1600x1200 60.0
1680x1050 60.0
1280x1024 60.0
1440x900 59.9
1280x960 60.0
1280x800 59.8
1280x720 50.0 60.0
1024x768 60.0
800x600 60.3 56.2
720x576 50.0
720x480 59.9
640x480 60.0
HDMI-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 531mm x 298mm
1920x1080 59.9*+
1680x1050 60.0
1280x1024 75.0 60.0
1440x900 59.9
1280x960 60.0
1280x800 59.8
1152x864 75.0
1280x720 60.0
1024x768 75.1 70.1 60.0
832x624 74.6
800x600 72.2 75.0 60.3 56.2
720x480 59.9
640x480 72.8 75.0 66.7 60.0
720x400 70.1

When I take a screenshot, the second screen looks OK so I can't actually show you how it appears to me. I thought the screen itself might be malfunctioning but if I enable that screen alone, it works like a charm. Even tried it on another pc (as standalone screen) and it worked perfectly.

On a sidenote: I tried the official nvidia binary drivers as well, there the second screen simply would not budge. It stayed black no matter what setting I tried. Fun fact though: if I take a screenshot with the official nvidia drivers enabled (and the second screen black), it still shows a proper dual screen setup.

If I recall correctly, on the previous setup (before the crash), I was using the proprietary driver but I'm not entirely sure.

On a further note: in light of this topic, I tried to start up the "displays" tool again at which point the desktop became unresponsive. I had to restart the lightdm service to get it back up.

Any ideas what could be causing this?