supporter internatinalisation broken

Hello,

I try to use supporter plugin, and make new locale. But rebranding and Premium Themes and Premium support messages are failed to set in this locale (on supporter/settings) because if í set Á?É?ÚÓ characters (utf8) the settings page makes conversion on these strings and i get unreadable words after reload settings page. For example: Ön közvetlen result ""Ã?n közvetlen" and this also altered if save again (specialchars or unspecialchars missing in this field this is not multibyte safe?).
Also problematic Rebranding (same error) if rebrand contains chars with accents like ÓÜ?? altered same way as above. Also, i get network name in paypal payment wrong encoding as above.
And unfortunetly i have some not translated expression (fe: Available Premium Themes) please check the default.po or pot to translate completely, thanks!
Please fix because english interface not acceptable to our users. Thanks!