[aiharkness]

You may achieve a temporary fix by holding down the trackball and at the same time rolling it in the direction it is stuck until it frees up. This is RIM's recommended fix. It may work, and you may go awhile before it sticks again.

You might look for online videos of the procedure to replace the trackball on your model BlackBerry. It is fairly simple. If you are game, then search for a trackball replacement kit. Be sure you buy a genuine BlackBerry replacement part.