Sounds like your using your Curve with dirty hands . Haha but you can certainly buy a new trackball and a new keypad unless if you want to dissect your Curve and try to clean it yourself.
I really don't bother with cleaning my trackball much. Once they start feeling loose and sticky(about every 6 months) I just buy a new one. A new one is about $10 and it feels...well...new.
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