Every once in awhile. It usually happens when it get dirty. You can always try and clean. (look around here and you will see a how to about it) or you could buy some. I know my VZW rep pretty could and so when my gets that way I will go into her store and she'll help me out. First time I got a new one and the second time they just cleaned it for me.
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You're not cool unless you're Snoopy cool
Trackball wont scroll down 
Linear Mode
