I initially came here to write about the passing of Tom Cheek (see item above) but on the way to doing a good thing, I ended up cursing my trackball. I actually love trackballs. Every computer I own has a trackball, rather than a mouse. Trackballs take up less space than mice and tend to not pick up as much crud and require less frequent cleaning. But there's a HUGE difference between less cleaning and no cleaning.
The trackball was SOOOO flighty that I broke down and unscrewed the bottom screw of the Logitech Trackman and popped out the big red ball. (I have Trackman marbles and even a Microsoft trackball in the house, but I vastly prefer the big ball type from Logitech.) I looked inside and wasn't completely surprised to find each of the pins that hold the ball in place were covered with a mat of lint. The window for reading the dots on the trackball was relatively clean, but the rotating pins were just buried. In all, I pulled enough lint out to form a good sized pea. THAT is gross!
I reassembled the trackball and faith and begora, the mouse started jumping to my commands like it always should.
Once more, trackballs require less frequent, BUT SOME, cleaning.