You have been disconnected from the server,

Hello guys,

I just wanted to check on Frostmourne, downloaded wotlk client once again, started the game and then.... "You have been disconnected" message appeared, sometimes it let me in to character section but it's empty and nothing can be done there and sometimes it just get back to main screen after a split second.
I have no idea how to fix this but it used to work just fine like 2 months ago.
I've tried setting compability, running as admin, checked WTF and realmlist, tried to log in on 3 different internet sources and still can't get in..

Any ideas what could cause the problem ? Thanks in advance for your help :)