Can you please find out, which entry in the FSX.cfg causes the problem?
This one (and, of course, doesn't have anything to do with any of our software, as usual...)
These are the default Simobjects paths, with FSX just installed:
SimObjectPaths.0=SimObjects\Airplanes
SimObjectPaths.1=SimObjects\Rotorcraft
SimObjectPaths.2=SimObjects\GroundVehicles
SimObjectPaths.3=SimObjects\Boats
SimObjectPaths.4=SimObjects\Animals
SimObjectPaths.5=SimObjects\Misc
And in your modified FSX.CFG:
SimObjectPaths.0=SimObjects\Airplanes
SimObjectPaths.1=SimObjects\Rotorcraft
SimObjectPaths.2=SimObjects\GroundVehicles
SimObjectPaths.3=SimObjects\Boats
SimObjectPaths.4=SimObjects\Animals
SimObjectPaths.5=SimObjects\AI-Planes_SB\Pai
SimObjectPaths.6=SimObjects\UT2 Demo Aircraft
See ? The Misc folder is missing. Instead of adding a new section for the SimObjects\AI-Planes_SB\Pai folder which is what it should be done, you (or the installer of that product) REMOVED the default SimObjects\Misc path and replaced it with the SimObjects\AI-Planes_SB\Pai path.
The Misc folder is where we put all GSX and scenery objects so, on top of losing everything with FSDT, this modification also killed a lot of default FSX scenery objects.
The correct lines should be as follows:
SimObjectPaths.0=SimObjects\Airplanes
SimObjectPaths.1=SimObjects\Rotorcraft
SimObjectPaths.2=SimObjects\GroundVehicles
SimObjectPaths.3=SimObjects\Boats
SimObjectPaths.4=SimObjects\Animals
SimObjectPaths.5=SimObjects\Misc
SimObjectPaths.6=SimObjects\AI-Planes_SB\Pai
SimObjectPaths.7=SimObjects\UT2 Demo Aircraft
Never, ever, touch the first 5 lines, only ADD after them, in sequence...