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 correct.
fixed. Will be released soon.