I'm IT at my company and have hands on with a lot of these device (dose not hurt to be 5 blocks from RIM either or that our company does media for them) I have a Bold that is from AT&T unlocked and i find that it is the same as my old Curve just touching the ball shows activity. I do know one thing though my device is rare as it was built in Canada so I'm wondering if they did some changes to the parts for ones made in different countries or. I also have another user in house that has the exact same issue that you have described. you have to put slight pressure on the ball to get it to take. i was playing with it and found it very hard to use my self as its hard too keep pressure on it steady with my thumb scrolling without clicking or not enough pressure. I wonder if this is a defect on some of them.