I hit the same problem "just yesterday" setting up my new BT, which I was on the brink of sending back.
After dilemmas with Bluesoleil, finally uninstalling it and letting XP handle the set up, mine works perfectly on com5
I got the same message from Arduino 9, and switched to 7... and 7 worked fine.
Needless to say, a port issue is possible, but the error message I got when it was a port problem, mac and pc, was "programmer is not responding".