Gtk background error of some type. I've actually seen that a few dozen times now on my own. It usually goes away if you correctly install the linux related GTK for windows.
Uhm you can download yourself a copy of of it somewheres or get it with another program. It comes with GAIM (Pidgin) now, a multi protocol Instant Mesenger I use. You could try to install that if you wanted to see if it helps.
http://www.pidgin.im/
Also you can try to use the in-game RC if you have the rights to even load it on the server your on. Uh, F6 I think it what you press.