Question marks mean that the font you are using doesn't support those characters. If you're loading Russian characters in the English client, and you're using the default Friz Quadrata font, you will get question marks. If you want to show Russian characters in a non-Russian game client, you need make sure the font you're using includes those characters.
Arial Narrow supports both Latin and Cyrillic characters.
The version of Friz Quadrata loaded in English clients only supports Latin characters, while the version loaded in Russian clients only supports Cyrillic.
The Friz Quadrata lookalikes used by Korean and Chinese clients support both, so if you like the look of Friz Quadrata, you might look into those:
Code:
2002.ttf 2002
2002B.ttf 2002 Bold
ARHei.ttf AR CrystalzcuheiGBK Demibold
ARKai_C.ttf AR ZhongkaiGBK Medium (Combat)
ARKai_T.ttf AR ZhongkaiGBK Medium
(Remember, every client includes the font files for every locale, even if it doesn't load them.)