Mouse motion speed

[manveruppd]

Hey everybody, something weird is happening and it's driving me nuts: my mouse cursor moves at different speeds depending on which application is in the foreground! For instance, in Opera it moves at the speed I set it at in the control panel applet, but on the desktop it slows down to a crawl! It's completely random and changes too (for instance, sometimes it moves at normal speed on the desktop as well, other times it's slow everywhere).

I tried switching off the "disable accelleration in games" option in the mouse applet in case thatwas what was causing the variation but it made no difference.
Any suggestions?