I've got the same mouse. It's great. Have you tried updating your mouse driver, Setpoint? Make sure you have the most up-to-date one, as tehy fixed some problems with the mx1000 last go round.
If that doesn't work return it to the store if you can, or RMA it through Logitech.
Just try the driver first, because if that's the problem a new mouse won't help you. :wink: