I just bought a 76CSx and have no previous experience trying to connect to my USB only laptop. Silly me, when I saw the USB notation on the Garmin literature for the 76CSx, I assumed it would function with the NMEA protocol. In trying to resolve connectivity, I came across GpsGate and thought my problem was solved.
After downloading the trial version, I could not establish a connection to the GPS. The proprietary Garmin software, Mapsource does connect.