Whenever I create or join a game I get this error, and the game shuts down when I try to do the tutorial...my firewall isn't blocking it and I reinstalled.
EDIT: I was viewing the French tech thread and found my solution thanks to their community and some online translation.
Not sure if a lot of people have this problem but what happened was I couldn't join games, create games, or play the tutorial practice dungeon. I fixed this by opening up a port, allowing 12227 UDP to not be blocked (this can be found in firewall settings, sometimes you have to click advance options). When you get this error, it basically means your computer is blocking you from the game network.
Great game, hope this helps.