Whenever I encounter a problem, I apply Hoarder’s Razor. This principle states that among competing hypotheses, the one with the most disgusting assumptions should be selected or when you have two competing theories that make exactly the same predictions, the nastiest one is the better.

Case in point; there was cat hair and/or some other gunk that I couldn’t see, in the recess on the underside of my wireless mouse, where the movement detection laser is. I crammed a damp kleenex up in there and pushed it around a bit, now the mouse performs as new.