I too can't update any of my iOS devices from home. When I try over the air updates they fail. When I try to download the full install, it just hangs forever "connecting".
On my 2nd gen Apple TV, I try to update I get "The Apple TV update could not be downloaded at this time."
Weirdly, it worked at work using their wired high speed network to update my iPad and iPhone. But I don't think I'm taking my apple tv there to update!
I know my Internet connection is fine - I just bought a TV show off of itunes. Could this be regional? I'm in Chicago.