when switching back to FC-3, mouse is erratic and unusable. Doesn't help to switch to text console (Control-Alt-F2) and back to X. Doesn't help
Drives me crazy and I actually had 2 mouses on my desk not plugged into the KVM but a friend said hitting the ESC key worked for him and I tried it, it works for me too. I have no idea why the ESC key would fix it but it does for my friend and I. By the way it started on FC2 for me.