I have a Mac Pro 1,1 2006 in which I have a small Bluetooth Dongle in one of the front USB connectors. I got a Magic Trackpad for Christmas but kept running into issues where the trackpad would stop responding for anywhere from 5 to 30 seconds. Sometimes it would hang up in the middle of dragging a window around which was a real pain because, even though the mouse was working it would just drag around the window. Couldn't click on anything until the trackpad came alive again. Also, although two finger scrolling worked on the trackpad as soon as I tried dragging 3 or 4 fingers on the trackpad it would hang up immediately. 100% repeatable. The mouse I was using was an old Logitech wireless mouse with a USB plug in transceiver. On a whim I unplugged that mouse and replaced it with a Logitech bluetooth mouse and.... the trackpad now works perfectly on all gestures including 3 and 4 finger. It has not hung up once since replacing that mouse. No idea why it was interfering this way and why multi touch gestures caused 100% hangup. Just thought I would post it in case there was anyone else in this situation trying to figure out if they got a defective trackpad.