My iMac's wireless mighty mouse is on the fritz. It scrolls up fine and side to side ok, but many times it is very erratic scrolling down. I looked for a way to take it apart to clean the little ball and surroundings but don't see any screws or a way to open it. Any help in getting this thing open or a fix to my problem is appreciated. Also, can anyone recommend a WIRED mouse to use if this one needs to go to the mouse graveyard. Thanks in advance.