Comment 5 for bug 355905

I might be experiencing the same thing on Karmic Koala Beta. I didn't look for the left and right options at first, so I cannot tell if they were there and disappeared. All I know is that it is gone now, leaving just the options 'Normal' and 'Upside Down' for Rotation.
The first thing I did was install the ATI/AMD FGLRX driver. It was then that I noticed the options for 90 deg Left or Right were missing. Tried uninstalling the driver but same symptoms. I'm trying to use xrandr -o to rotate one monitor but need to figure out what it calls the display. Will research that myself.