Before you do anything drastic, make sure your mouse pad doesn't have too many lines and stuff on it (honestly :P) which is pretty much what D0pp139an93r said. I use part of a map that's on my desk as a mouse pad and because of this the mouse sometimes jerks from side to side, goes in the wrong direction, etc. I'm just too lazy to get rid of the map.

And yes, the mouse is fine when it's not on the map.

ac