Since this morning's update was released, the Steam network has been overloaded, causing many Steam users to be unable to login.

Until the Steam content servers are able to catch up with demand, some users will continue to experience slowness or unresponsiveness from the Steam client. We've been making some changes to the content servers today to accelerate this recovery, and we expect conditions to improve quite a bit by tomorrow morning.

Thanks, again, for your patience after this update.