All of OS/2 world really should be using UTF-8 by default, so some reason it is set to Western by default which is making firefox render all international chars as garbage.
Noticed myself, thought that this was solved, and i'll look into it. Problem is that Joomla 1.0.12, as far as I read, doesn't support UTF-8. SMF forum supports UTF-8 and I don't know if this managed to get some kind of mixture here.
Found a parameter in the smf forum settings file that was enabling the utf-8 coding, disabled this so I hope that it shouldn't be an issue anymore.