A bit fed up not having any feedback from PMDG people, I kept trying things and I eventually managed to find a solution.I had a strange feeling that my initial JS41 installation had messed up in the registry. I knew it could be solved in uninstalling and re-installing FSX again. However, I had too many addons installed and I didn't want to touch my stable configuration.1/ I deleted first my PMDG MD11X and JS41 (actually delete all installed PMDG aircrafts),2/ I cleaned up the registry with CCleaner to remove orphan keys and declarations,3/ I removed all keys and values related to PMDG,4/ I re-installed the PMDG JS41and everything went fine. I got my JS41 working again. I hope now it will last for a long while.With the hope that it could help people in a similar situation.Cheers,Pascal.

Thanks for posting the fix. And just for reference, the only way to get help from PMDG directly is via email.

Hello Dan,I thought that Ryan or somebody else from PMDG could have relayed the request as they are several at PMDG to watch such fora.Pascal.