FWIW, many problems with mice can be tracked (pardon the pun) down to two things: one is a loose connection at the back of the computer, the other is dust/dirt inside.
http://www.helpwithpcs.com/maintenance/mouse_problem_maintenance.htm

Often times, a good cleaning can make a mouse seem like new.

[This message has been edited by ThinkGood (edited 09-02-2003).]