QUOTE(weelad @ Nov 19 2010, 04:01 AM)
Think this may be already answered in a different topic,
Connect to the Internet and use a profile that has not downloaded the media update before (create one if needs be) try to play file, download update, then play file, disconnect from live, switch profile back and play file.
Worked for me.
what happens is the media update is locked to the first console its downloaded on with a given gamertag, and any subsequent consoles will need to be online and logged in with that profile in order to use the media update