Sounds like something is wrong with your comport setup on your carputer.
The GPS doesn't require any drivers. it's just a normal serial device. For me, under WinME, windows didn't identify the GPS at all. All it cares is that there's a serial port. WHat's on it, it could care less about.
Hope you can figure it out -- again, it's probably a problem with your com ports, not the GPS. I'd try removing the com ports and readding them.