Make sure there are no pieces of fuz or dust in the mouse sensor area

While you're at it.. A common problem with optical and laser gaming mice odd movments is due to the mousing surface getting shiny from use, or there are contrasting colors/shades on the surface that read funny when the mouse is moved over them..

Try using a different mousing surface, a darker material, or less reflective surface, so the laser does not bounce off the surface and back into the sensor when it is lifted off the surface to reposition the mouse.

If your mousing surface has become "polished" from use, if it's a cloth surface, clean it off with a slightly damp rag/mild dish washing detergent and let it dry completely before using it again.. also wash your hands well with a good dishwashing liquid detergent etc before using the mouse, that way there will be less hand/finger oils to rub off onto the mousing surface... You got a solid surface? a good scrubbing with some dish detergent and a non abrasive dish-scrubber can cut down on the "polish/reflectivity"