So far I haven't been able to connect to a single game through the lobby. I can join lobbies, use and hear voice chat, but right as the counter reaches 0 and the game starts loading, I get stuck in an infinite connection loop. It tries to connect, I get "connection attempt failed", waits 5 seconds and fails again. The return to lobby button doesn't work either.
I have to ALT+F4 out of the game, restart the game, and press the reconnect button in the main menu. Then it joins the server in less than a second. I can also join games by having a Steam friend join a game and using the "join game" option in the friends list. Voice chat works fine in-game too.
I have disabled Windows firewall, PeerBlock, COMODO firewall, and Avast antivirus. I still cannot join games through the lobby. I have also forwarded the following UDP ports through Windows firewall and my router:
5055 to 5100
27000 to 27030
Speaking of PeerBlock. Whenever I'm trying to connect I get bombarded with ~4 pings/second from DINSA Ministry of Defence from IP ranges starting with 25. According to this: http://b.logme.in/2012/11/07/changes-to-hamachi-on-november-19th/
it has something to do with Hamachi. I do not have that program installed.
I happened to reinstall Windows 7 last week so I'm on a fairly fresh system software-wise. To make things even weirder there's a roughly 10% chance of Firefox/Chrome or Steam web browser working while have the game open. Other application's online features work just fine (instant messaging etc.) but anything that is browser, more often than not, does not. I've managed to open a web page a couple of times but almost always the browser complains that there's no internet connection. Windows' network and sharing center shows that there is a connection.