Much to my surprise I am unable to log in with my user name "Michael Müller" I use now 11 years or so. Tried with this old one I used before, and had to realize that the board software does not accept non-standard letters anymore. My name is now shown as "Michael M�ller".
Well, that means I will stay out of forum until the bug has been fixed.
This has been happening ever since the whole board crashed back in June. It appears a lot of the customization - charsets, search tweaks - has had to be removed in order to make it run at all.