For what it's worth, I can't connect to my server through the lobby after today's update. My server just crashes. You can see the error messages here
http://forums.steampowered.com/forum....php?t=2474262
Before I get the crash, I do see a message that says
* Unable to load Steam support library. *
* This server will operate in LAN mode only. *
That may explain your error message.
I have found a workaround for my crashing by connecting through the group server at the bottom of the menu and then changing cvars in game and directly forcing map changes. It probably won't help, but you could try joining your server some other way.