My opinion is that you should alter some tables in mysql, the tables that holds that information.
Example: mysql_table -> sb_bans -> name
Hit edit and change "collation" to that you want. I think cyrillic should go with koi8r_general_ci ...
More info here:
http://www.java2s.com/Tutorial/MySQL...aracterset.htm
Try changing just that table, add a fiction ban and refresh the page. See if it's working (just for the name) If it works, you sould manualy find and alter all the tables that holds cyrillic chars.
If it's not from the mysql database, you should change some values in webscript (don't know which one though..)