just bought an new iMac with a wired mouse. It works ok most of the time and then jumps on the screen. (will jump from one place to another on or off screen for no reason) Diagnostics with Apple concluded that the mouse was bad so they sent me a new one, now the new one is jumping too. Is there something wrong with these mice? Could both mice have been bad or is it something else? OS or computer itself. I have a logitech wireless that seems to work ok but the mouse from apple doesn't. Any suggestions?