Its very likely Jeans Pockets are messing with it. Think like this:
Jeans are meant to be tight very often. Whenever I wear my BB in my Jeans Pocket, I pull it out to find "Qjwwwjdkskjsj Hjkd Ajfd" on the dial input screen (lol). The point is, they buttons get pressed. Perhaps the tight pocket is pressing the TrackBall in for long periods of time, so the previously mentioned "Copper Spoon" is getting bent in and stuck.
My two cents.
"This must be Thursday. I never could get the hang of Thursdays." --Arthur Dent