Character Sets

Can anyone explain which character sets can I use in file names and in tags with my m250? My native language is Russian and I live in Israel, so I’d like to have possibility to view both Cyrillic and Hebrew characters. I tried to load mp3 and wma files with both sets to the player but results were a little bit strange. If mp3 file name is written with Cyrillic letters and there is no tag, file name is displayed correctly. If I add Cyrillic characters to tag, m250 ignores the whole tag. In wma files I can use Cyrillic characters both in name and in tag and all is displayed correctly. Hebrew characters I can’t see at all. I tried to use Unicode.

Is there anywhere any explanation about this issue?