I had the same error, then just now I went to the Franson GpsGate 2.6 (v188.8.131.520 demo) icon in my start menu, and did Right Click -> Run as Administrator and it appears to have worked! You just need administrator permission to create "virtual COM ports" as I would expect. I'm running Vista Home (32bit I believe) on a Dell laptop from summer 2007 (XPS M1210).
== Debugging ==
On the Output tab of the Settings window, I added a "Virtual COM port/Garmin Emulation" for my Vista Cx and it said it worked, and now "1 client connected" from GooPs set to COM4. However, my location is not being feed to Google Earth... it still says my lat/long is 0/0.
How else do I debug this and see what Lat/Long coordinates my GPS is sending? A "Debug" tab would be nice to have a scrolling log of the traffic being communicated to the Virtual COM port. How about Outpt to a text/log file?
I have GooPs set to Port: COM4, Rate: 4800, Flow Ctl: Xon/Xoff
Garmin Vista Cx on Windows Vista Home