If the apple mouse becomes old normal cleaning of the small scoll ball with a moist cloth does not help any longer. For mine the following procedure workes: (1) Rinse half a spoon of spirit (pure alcohol) over the scroll ball. (2) Instantly turn the mouse upside down and let the spirit leak out. (3) Turn the mouse back (upside up) and wipe the scroll ball with a dry cloth Normally the mouse ball is ok again after 10 to 30 seconds wiping. In rare cases I had to clean the ball twice.