When you first start a chat, and not just bad - disabled plugins. Go to control panel, manage plugins, save the settings.
But I do not understand: In the chat did not write 'кирилица', 'abcdefg ...' - ok, '123456 ... ' - ok. The same is true in 5.4.1 - still not understand what the case may be encoded in the base. If you find the problem please.