The Track ball is a little delicate. I washed my hands.....dried off well.....and went to check my emails.....and now it does not allow me to scroll up. I can go down......and sides.....but once down....i can't get back up to check my emails unless i take the battery out........to recycle the thing. Just a little FYI to let your hands get completely dry and free of any moisture before touching the track ball.