Details
Description
It seems like transforming from certain character sets to utf-8 does not work: cp1251, cp1250, koi8-u (locale ini files for Czech, Croatian, Russian and Ukrainian). Might be related to http://issues.ez.no/8969 . When the PHP extension mbstring is disabled, the range of character sets which can not be transformed to utf-8 gets bigger (about everything that's not utf-8).
Symptoms: the language names are not displayed in the "Language options" step of the setup wizard. You only see their checkbox.