I’m using a multi monitor setup on a ATI 5850. Sadly I often experience that my mouse pointer gets corrupted on my primary monitor. It seems like there is no immediate fix, it’s a known ATI-driver windows compatibility issue.
But there is a solution, that will make the corruption go away (it’s not a permanent fix sadly). But all you have to do is to open the magnifying tool in windows. This can be done by typing “magnify” in you RUN window, leave the magnifying tool open at 100% and the corruption is gone. When the tool is closed the corruption reoccur, so no real fix, but at least faster than rebooting your pc.