While I like this game a lot, there are a lot of bugs.
I've figured out a way to register - click OK and then click register very quickly. After clicking 'OK' again two times you should get a message saying "register successful" or something around those lines. After that you're ok to go.
However, you still have a popup message while you're playing.
Aside from that, you should be able to toggle between languages (for interface) and have different servers for Russian players and English players.