Keith don;t fret too too much about the Imac man, with all the popularity I sure there are bound to be the occasional issues with a couple. I think you got some possible i/o issues connected to the USB chain. I can bring you another usb mouse if you'd like OR just take that puppy back for a replacement unit..... call ahead to make sure this can be done hassle free to save you blowing your, or someone else's, brains out at the store. I've got 40 of those bad boys out on the floor and not a single issue like yours in the bunch of 'em. I checked this morning and they are indeed running the default mouse KB setup as well. You may be being punished for not keeping up the the Kashmeri's...just a thought.