Sorry all for my unresponsiveness.
I had no idea this thread was still alive (I must have missed the notification email that this thread has been contributed to).
I did a Google search trying to debug some issues w/ XPort and came across this thread...and to my surprise it is still alive!
Sorry to keep y'all waitin.
I have been bangin my head against the wall trying to figure this one out.
stang: Are you using XPort too?
I have rewritten *all* of the COM port GPS code w/ a 100% C# library; my C++ gpscom.dll code is a thing of the past.
Even after the rewrite I still get a "The request is not supported" error when I try to open a XPort COM port.
I guess I am going to have to write a small native C++ test app to learn how to properly open an XPort port.
Again, sorry for the delay.
My Car's CFMapPoint ain't workin either, so I am feeling the same pain as you.
My problem is a bit different though; I am not using XPort...and worst of all it *used* to work!

Without changing anything in CFMapPoint itself, my CFMapPoint just stopped working correctly, no more GPS or Routes or anything.
The only change I made were some Windows Updates, so again I am blaming them!
Please be patient; I am workin on it.
Hopefully the fact that I wrote CFMapPoint in the first place will show you how much I want this to work.
Alas, I am only one person and I have a life outside of CFMapPoint so sometimes it is hard to find the time.
The source code is available for anyone else that wants to pitch in.
The best thing someone could do would be to write a "hello world" C++ app that can open an XPort port and read from it for a few seconds.
I know how to do this for standard ports, but the XPort ports are causing me a headache for some reason.
(I assumed they would accept the same standard COM port code...they currently don't appear to).
Pv