We’ve just put a small update out that should hopefully solve some of the DDOS problems we’ve been having over the last few days (fingers crossed!). Thanks for everyone for their help with this, especially everyone that emailed in information, Steve from Multiplay for his feedback and analysis, German Hoeffner from Ideal Hosting for his debugging and advice, and of course the MuchDifferent guys for their swift fix.
Servers will need to be updated before you can join them, and your client will obviously have to be up to date. If your client isn’t updating try restarting Steam.
Thanks for sticking with us and being patient while we’ve muddled our way through these issues. The servers aren’t bulletproof, but hopefully we’ve made it a bit harder to completely take them down.