I've got one such pixel on my PowerBook that's been that way since 2004. A couple of pushes on the front or back of the screen and it will go away. It's something I used to have to do every month or so when I first got the machine back in 2004. But in the past couple of years I'd be surprised if I had to do it even once a year. I can't even remember the last time it got stuck actually.

Don't underestimate the power of the pixel massage. Its benefits are obviously cumulative. A sort of pixel rehabilitation.