I just upgraded from Ubuntu 10.10 to 12.04. I had been using a display configuration just like the one described at http://bitkickers.blogspot.com/2009/08/rotate-just-one-monitor-with.html without any problems under 10.10. I have an nvidia Quadro FX 380 and have upgraded to the latest drivers (295.49).

Everything appears to be fine when the system first boots up. However, after logging in, the left screen goes black, and the right screen displays what should be displayed on the left screen. Logging into Ubuntu 2D somewhat improves things. The left screen correctly displays the left portion of the desktop but the right screen contains a duplicate view of the left screen.

Turning off Xinerama and enabling TwinView appears to fix the issues but does not allow the right monitor to be rotated.

Since the display problems start to occur only after logging on, I thought it might have to do with carryover user configuration from 10.10 but the problems persist even when logging in as a guest.

Clicking on System Settings -> Displays results in the error message "Could not get screen information - RANDR extension is not present."

Any help would be greatly appreciated.