Issue: Search doesn't work with languages other than english

We have Russian language on our forums, but a search function in VW doesn't work with UTF8 symbols other than english.
I noticed that problem in a main search box and in the category selection box.

For example, if I type "Search" a system displays me results, but when I type "Поиск" (russian for "Search") it displays nothing and "Starts with: %u041F%u043E%u0438%u0441%u043A". So utf8 characters are not parsed. This means that I cannot search on my language and I cannot select any category for the pages, that titled on my language.