Garmin Ique 3600


I have a Garmin ique 3600. It will only operate on windows, so I have virtual pc 5. This works fine, running on Tiger. What does not work is the sync option. I constantly get an error message that the unit can not connect to COM 1 or COM 2, as it is looking for a serial port, even though the unit is connected through a USB port. When I attempt to change this in the preferences, it says that there are no serial ports available. Is there any way to sync this unti with virtual PC?