I have had the same problem after being kicked out of server suddenly. I tried restarting the game, restarting steam and restarting my computer, none of these helped. This answer might be late for you, but it can be helpful for other people having this problem.
Solution is to flush the DNS cache by running "cmd", and typing:
ipconfig /flushdns
This one worked for me. But flushing the DNS cache may bring problems for you, I am not sure about that.
But the way to flush differ for different operation systems. This one works for Windows 7.