HANDY LINK ALERT
Try this site before you order a new trackball or remove the one you have now.
Also, be very careful with the retaining ring if you do remove the trackball. They are easily broken when removing or installing. ALSO, I highly recommend have a spare ring before you remove the old one. They are cheap on ebay. Pick up a trackball too...can't hurt to have a spare I guess.
The strawcleaning trick that worked the best for me was the one with the split straw end the "wings" method. My trackball is really like new again.
Thank you mr/ms poster at http://unique-stuff.co.cc/fixing_sticky_blackberry_trackball.html