Q: The tracker ball on my USB mouse has stopped working.Any help would be appreciated.

Hi Mick,

http://www.apartmenttherapy.com/how-to-clean-apples-mighty-mou-108357

http://hints.macworld.com/article.php?story=20060210115417864

If the scroll ball on your Mighty Mouse has become discolored or dirty, use a clean, lint-free cloth lightly moistened with water to clean it. Wipe the ball and the surrounding area, making sure to rotate the ball itself to ensure complete coverage. If the scrolling feels rough or if the scroll ball isn't scrolling up, down, or side-to-side, hold the Mighty Mouse upside down and roll the ball vigorously while cleaning it to help dislodge any particles that may have collected on the internal hardware. Watch a QuickTime movie demonstration of this procedure. (The movie is approximately 600 KB.)

http://support.apple.com/kb/HT3226