There was a note recently in
this post about a comport related error in the Airmail script and how to fix it. Not sure if it will remedy your issue but worth a try.
While you're at it also check that you have the correct comports script which is decribed in
another post (the comports script is called by the Airmail script).
I remember having the same issue that you describe a while ago, but Pactor with USB worked fine and I didn't bother to get to the bottom of the Bluetooth issue then. Now I no longer have a Bluetooth capable laptop...