I ckecked for a patch named scale, but couldn't find one with this name. It's also happening when I want to make a new scale object. It's not possible to create a new scale object. I tried it in Max5 and Max6.1. It's working in 5, but not in 6.1. See added screenshot.
I think that was the probleem indeed. I fell from one problem to the other with checking for a scale file in the search paths. Had to reinstall Max to get everything right again. Let’s say, lesson learned.