one post leads to the other...
So I tried to edit the PRJ-file, but then decided I would not edit it,
rather redefine the whole project with only the files I want in the order I
want them. OK, said and done. Then I wanted to exit (no unsaved files), but
I just get a msg "File is being edited" and I am returned to the
edit-session. Neither the PRJ nor its DAT are being edited, so I wonder
what this message really means...
So I removed the auto-save, quit, restarted, redefined the PRJ and now was
able to save.