Actually, the activity process of the Scroll Box looks very strange… All of the messages included in box are shown without any problems on Cyryllic. As for “Thank you” tab (mentioned ago in my message), it looks something absolutely odd in Admin page after updating this page (abrakadabra), but often shows this message ok in Cyrillic the first two-three times for visitors, and then again it breaks something and it shows like on Admin page – namely absolutely abrakadabra.
Bytheway, all my code page settings on the site UTF8. Maybe my theme does some damages some settings?