You missed the point, entirely. I'm not saying "your FSX is unstable", please re-read my previous message carefully:
I've said that, if you check for buildings immediately after you got a "3rd party module", regardless which module the message related to, it will not probably work because, after having issued such message, FSX is in an unstable state FOR THAT SESSION, which should have been obvious from the next sentence, when I've said you need to first be able to launch FSX without message, before checking for buildings. Since you said you "immediately" checked for buildings at KJFK, my reply was ONLY to explain that it wouldn't work in the same session the 3rd party module message was issued, NOT that your FSX has become permanently unstable!!
Usually, a Windows reboot should fix the issue.
However, there's a very simple way to check if the problem is that our module has somewhat created a problem that makes FSUIPC failing.
If you open your DLL.XML file, located at:
%APPDATA%\Microsoft\FSX
with notepad, and go to the Addon Manager section, that contains a bglmanx.dll reference. Set the <disabled> line to be like this:
<disabled>True</disabled>
This will disable the Addon Manager entirely.
You can do the same for the Couatl module, although it doesn't seem to create issues to you but, just to eliminate any possible doubt, open your EXE.XML, located in the same folder, and set the <disabled>True</disabled> line for the line that contains the Couatl.exe reference.
Save both files, then launch FSX.
This will run FSX without ANY trace of our 2 modules. They can ONLY be loaded this way, if they are not called from the XML files, it would be exactly as if they were never installed.
If you are still getting the FSUIPC 3rd party module error, than IT'S SURE that this error doesn't have anything to do with our modules.