The number 1 cuase of mouse malfunctions is dirt build-up on the rollers....take the ball out and use a small,sharp knife to scrape the crud off of it.
then use a bit of compressed air to blast the crap out of the mouse....(got to wal-mart and get a can)...
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Mein Ehre Heisst Treue
Das Geminschaft
2nd SS Panzer Division