Have you tried the obvious? Using a different mouse. Yours might simply be worn out, and not tracking properly anymore assuming it's an optical mouse. If it's a really old ball mouse, then it's entirely possible the ball and/or rollers have started wearing smooth and there's less friction to register as mouse movement. Considering mice are relatively cheap, and having a spare around is rarely a bad idea, I'd suggest starting there.
Many people report a problem in Vista, with the cursor suddenly jumping backward or forward on a page, or especially when composing in a text processor.
Most answers address laptops with touchpads -- but the problem also occurs on desktop machines with mice, and I'm not seeing any solutions for this case.
I have run the System File Checker, as well as Microsoft Security Scanner, and the Microsoft Office file repair utility, and additional malware sweepers as well.
Nothing solves this irritating problem, which cropped up suddenly a couple weeks ago. I don't perceive any relation to the addition or upgrade of any program.
This cursor jumping is resident in Vista, and infects any program running under Windows, and most annoyingly in any typing-intensive program such as Word and Outlook.
Does anyone have insight or a solution to this problem?