HI - This is my first Mac user problem posting going back to my original SE! Power PC based imac running leopard 10.5.8 starts up but then mouse freezes after a few mins... Managed to change sleep mode to 15mins - same problem. Can't boot from Disk as same problem, also command+option and shift all still have mouse unmoved! Obvious change of keyboard and mouse have no effect. Could this be related to offspring's addition of ipad plugged into usb a few weeks back? He tends to unplug the device without ejecting! Any clues apart from replacing motherboard would be great!!