I am running Ubuntu 10.10 x86, 32-bit with the latest updates and ATI Catalyst 11.4 (latest version). When I rotate my monitor (1600x1200) to a vertical orientation (1200x1600), I can no longer properly move my cursor to the right edge of the screen.

When the cursor hits the right edge of the screen, it snaps back to the left by about 2 cm (~80 pixels). The window manager then appears to think that the edge of the screen is now at this position, so I can no longer move the cursor to the real edge anymore.

I tried rotating the monitor using both ATI Catalyst control center and the Monitors preferences control panel in Ubuntu. They give the same result. I also tried updating ATI drivers.

The funny thing is that I have a nearly identical setup on my office PC, and I don't have this problem.