Hi again Umberto,
I just want to say thanks a lot for Your kind help ! I've never seen such a great personal support like this before !
Everything works fine now.
For those users, who had observed the same behavior at their system :
The bug was at my FSX.cfg; there was missing the line to the path "SimObjectPaths.X=SimObjects\Misc"
Thanks again
and best regards !
Dietmar