Ran into this problem a while back with a 1 tuner source but recently ran into it again with a HDHR Duo.
While I was recording another TV show, I couldn’t use the Ch Up or Down buttons, every channel change would result in an All Tuners in use screen.
Does channels use a free tuner to start loading the new channel before discarding the old channel?
Could there be an option in the tv sources settings to choose between fast switching (using a second tuner) or slow switching (close tuner before attempting to open another)? This could help single/low tuner setups aswell as high recording setups.