Quote Originally Posted by frogbeastegg View Post
That's a nightmare I've had a few times. Got to love that loop of "Error: must be online to go offline".

I managed to work-around it once by turning my router off. For some reason that made offline work as intended instead of grumbling that I wasn't online. Worth a try, if you haven't done that already.
If steam fails to find an active internet connection after a few minutes it will ask you if you'd like to enable offline instead. That is, when it's feeling like it. As much as I like steam and use it daily, it is incredibly finicky about when it will let you go offline