Remove the battery (or power the device off / put it in sleep mode), then press on the trackball and scroll up. Do this for a minute or two. This should dislodge whatever debris is under the trackball.
The difference between stupidity and genius is that genius has its limits.
When you take things for granted, the things you are granted, get taken.
Even a mosquito doesn't get a pat on the back until it starts to work.
Too many people miss the silver lining because they're expecting gold.
[BES 5.0.3 / GroupWise 2012 HP2]