Thanks, I did rename intrface.bbw and MySetup.DK. Then I checked and adjusted preferences and options. Since the styles were empty I did a (slow) rebuild. In the the middle of this process the "Division by zero" showed up and I have the same status as before.

So maybe (one of?) the styles is corrupt?
Or may be installing the program in C:\Program Files (x86)\bb was no good idea (I set "Full control" for all users)?

Strangely BiaB VST in Cubase 12 works with no problems.

Thanks again for your ideas.
Gery