new hd patch

I'm trying to play on HD, but do not see any lobbies. I worked out that this is because there's a new patch, and I'm still on version 5.5. My steam does not update to the new patch for some reason.

I remember reading somewhere that you have to rename some files for the game to update to the new patch? I'd be grateful if someone could remind me what to do. It would suck if I can't play this game any more!

cheers