I would start by uninstalling both versions, trashing preferences and then re-installing FileMaker 13. If it is too much, try to uninstall FM14 first and then try 13.
Thank you, sadly that brought no improvement on FM 14 - it did not seem worthwhile reinstalling 13.
Curiously, there following message is presented if I drop an .fmp12 file onto FM14:
The document “Bezirke.fmp12” could not be opened. FileMaker Pro Advanced cannot open files in the “FileMaker Document” format.
I have a feeling, it is not FileMaker app you are having a problem with, but a file in question. Try to open another file.
Your file could be corrupted and you will need to go through recovery process.
Thnx, but I have already tried several files, which I know work.
I think you are right that it is not the app that is the problem, I am just hoping someone has come across this situation before and knows what to do with it.