Maybe this isn't your problem, but I had a world of trouble and found my Garmin Data cable bad. A new one fixed that problem, but I have to make sure the right serial port is selected almost every time I boot up. If I leave the Belkin or Keyspan adapters plugged into the USB port and the device cable (GPS and Palm) they seem to keep the port #. Matching port #s has been my problem and solution. Lou