Microsoft Intellimouse Explorer 3.0

My mouse recently started acting up. Pressing the thumb buttom on the left side sends you back two or more pages, rather than just one. I have had this mouse (or one like it) for ages so it's not an issue of getting to know my mouse. I have re-installed the drivers and changed the settings a bit to slow everything down, thinking that may be the problem. Nope.
I rencently had to install a new hard drive, so I started off fresh - the dang mouse still does that annoying back up two pages thing.

Any ideas? It's not a real big deal, but at times when I am on a secure site it will back me all the way out of it. Using the arrow on the browser window works just as it should.