Got a laser optical mouse that acts all weird? Check it for a hair stuck in front of the diodes. I know this seems obvious to look for obstructions, but this mouse has a sort of double diode arrangement and the hair was white.
It was hard to distinguish from the white reflections on the glass diodes.
Further, it was mostly inside the case and stuck out across the diodes, so it wasn't immediately obvious. It took some tweezers and some wrangling to get out.
I've gotten over $200 in cash back from them at places I would have shopped anyway! Ebay, Staples, more! I put it at the top because they ROCK. Basically, you get a kickback from Ebates when buy.com or whoever pays them. Win-win. If you like throwing money away, don't use them!