At the startup AP found two doule images in the Image database and when I opt for their removal AP no longer reacts. Clicking on the window causes the APPHANG message to appear. Waiting for AP seems to take very long (I haven't had the patience to wait very long yet), so I opted for quitting the application.
A second try went exactly the same. (my database is over 700 Meg: if needed I can send it to you on a DVD)

This is probably caused by the VACUUM command that runs after duplicates are removed. I will remove this (it can be fired off from the Image Preferences).

Fixed.