Hello Urs,
I did a complete reinstallation with the Installation files you pointed to. It worked! Thank you very much for your support!
I think it was the Server Installation that caused the Problems. With EFB1 I sometimes had to delete the index file to have a proper database. Could this be a possible solution in the future? During inspecting the server folders I found an index file for the Server.
Concerning reinstallation I have a suggestion: Before or during deinstallation there should be a warning, that all files in the client folders will be erased without warning. I put a lot of files into the library. I had a backup from where I could reinstall, but some flightlogs were lost. This took me by surprise, because in most cases reinstallations will keep customized folders.
Aivlasoft EFB2 is a great application. Having to fly without it worked but it was much more inconvenient.
Thanks again
Michael