EDIT: Clarity. EDIT2: Its been a couple of days since I posted this, all should be good.

I've just migrated some backend servers, which means that some IP addresses have been changed.

Most notably voxelturf.net has been moved to a new machine so things like server list lookup ("Find Server") may go to the old server instead of the new one.

Once the changes propagate though the DNS servers they should all be good. This typically takes a few hours to take effect, but depending on your ISP this could take up to 48 hours.

If you are having issues trying to host/join a friend's multiplayer game due to it not appearing on the Find Server screen, you can get around it by connecting to the IP of the host via Direct Connect, or by joining a game via Steam's Join Game or Invite Player functions.

Cheers,
Twigz