I did an upgrade from 5.8 to 5.9.
I chose Finnish for the install language.
It looked like either the install program didn't use the
right character set (iso-8859-1) or there was something
wrong with the text translations themselves: The letters d
and v (a-diaeresis and o-diaeresis) were replaced with some
weird characters everywhere in the texts.
Once the upgrade was finished, the character set was
fixed. Will be released soon.