Laser Mouse not tracking properly

I've had this Logitech wireless Laser Mouse for a number of years and it's been great but lately it hasn't been tracking properly. The mouse pointer skips and halts when I move it, and forget games! I've replaced the batteries, turned it on and off again, re-established contact with the base receiver, blew onto the lens to clean it of any debris (heh, I probably got spittle all over it), but nothing seems to work. It can't be that the laser itself has gone bad, has it? I do have a replacement mouse, but it doesn't have the thumb buttons on it that I like to use for my games. Any other suggestions? Thanks!