I have a can of dust-off at home. I spray air into the ball while gently pushing on it and moving it around. This took care of the problem the 3 or 4 times it got goofy on me. The trackball can also be gently removed (research before doing) and cleaned. I recently wanted a reverse keyboard color setup from the one that came with my Bberry so I got a new keyboard cover and trackball setup on eBay. Exchanging it out was easy and only took a few minutes.
I removed the trackball and cleaned under it and I cleaned the trackball itself. When I replaced it, the trackball would now go up, but not down. So I had an idea... I reopened the trackball and replaced the internal unit upside down. Now it only goes down again and not up. Side to side is still no problem. Does this sound like I need a new trackball, or can I fix this?
When I clean my trackball I get a qtip and dip it in rubbing alcohol, then I squeeze the qtip so there isn't a huge amount of alcohol on it and then roll the ball around with the qtip. You have to make sure the qtip isn't soaked though or you might mess up the electronics.
It working again! I just kept going right and left with the trackball and then I started trying to go up diagonally at the same time. All of a sudden it started going up. Now it works perfectly, with great response. I already have a spare housing. I'm going to order a spare trackball right now, just to be prepared.