Q: Why national characters are broken at JoomlaStats?
A: From version com_joomlastats_v2.3.0 We have introduce a functionality that will convert translations from UTF-8 to page encoding (usual iso-8859-1). This is realized by using PHP functions iconv() and/or mb_convert_variables(), but to use that functions You need to have iconv*.dll and/or mbstring*.dll installed. If You have not got 'Iconv' nor 'Multibyte String' extensions in PHP installed we are unable to convert encoding.
Solution 1 (Recommended): Consider installing 'Iconv' and/or 'Multibyte String' PHP extensions, due to Joomla 1.5.x CMS uses them to convert texts. We convert texts in very similar way like Joomla CMS does.
Solution 2: Convert files with translations (language files) to encoding that is used by Joomla CMS for that language.