can somebody point me to the thread or URL for replacing the track ball on the flip? Thank you.

Does the trim ring around the track ball look like it comes out.

Well, everything looks rather normal, but the trackball/cursor only goes horizontally, not vertically. My immediate reaction was the hardware. Would this be software/OS related problem? the phone is rather new.

for those who might want to know the how to replace it, this url will help:

BlackBerry Repair

How old is it. Try locking the keyboard and press firmly on the ball and scroll it around. Possibly has lint in the ball.

Wow, it worked - thank you so much for your great hint!!!!!!!!!!!!!!

Is the trim ring around the trackball not removable like it is on the Pearl?

It appears that the OP got his problem solved already.