Gary, I am certainly no expert in anything regarding computers, However, it sounds like the mouse might have some dirt particles embedded.

Solution #1, try cleaning the mouse.

Solution #2, go down to one of the big outlets-Comp USA, Best Buy etc. (avoid Fry's) and purchase a new mouse for $1.99 or so that they usually have on sale.

I understand the mouse Gene is talking about works very well, but for the price difference, one can buy an awful lot of chips.