Hi Umburto,
Since the last post, I have not yet had time to do as you suggested and remove KORD, the Addon Manager, and Couatl. However, I have since purchased the KSFO from FlightBeam, and activated it. It works fine.
Now that I am again turning my attention to the missing buildings in KORD, my question before uninstalling the above is whether any of the KORD, Addon manager and/or Couatl will affect my FlightBeam KSFO being activated, and if so, how should I deal with that?
What is happening now is that when FSX boots, I get an error saying that "The Couatl Scipting Engine has encountered an error when loading addon OHare X, one or more files may be outdated or corrupted"
Thanks again for your help, Bruce.