At many computers everything works fine with the same version of Outlook.
At this specific one computer (something installed wrong?) this problem
relates only to the forms - also VB created forms have diacritics characters
corrupted.

Values when filled in manually are kept unicode even at this "wrong"
workstation.

the question is, why and how to fix, e.g. what to install at this single pc
:-)
the solution is working at many versions of Outlook and many other pc's


Either Possible Values doesn't support those characters or the combo box
control itself doesn't support them. It's a very old control library, so I
suspect it does not support Unicode fully. It should be easy enough to test
that theory by using AddItem code to fill the rows instead of Possible
Values. See http://www.outlookcode.com/article.aspx?ID=32 if you're not