Hi,
I've tried many versions of Ubuntu (13.04 x64, 12.04.2 x64, 12.04 x86) and Mint (14 x64, 14 x86) and can't seem to use the multimonitor functionality. When opening my session using full screen, either single or all monitors, it displays the session full screen on the current monitor. When changing modes from full-single to full-all or vice versa, I get a cropped display of my desktop. Changing mode to the original setting doesn't revert the display crop. I'm uploading the log produced.
I've also had results of fullscreen single monitor working correctly, but upon changing to all monitors, I get a second display but the primary display is moved from the right to the left monitor.