I have two AppleTVs that I have been using, without problems, for the past year. Recently, however, the AppleTVs will show up in iTunes whenever I first open it, but after a while they disappear from iTunes. When this happens, I can no longer play anything which has not already been synced to the AppleTV (I will instead get a message that the "selected video could not be played. The format was not recognized."). If I close iTunes and reopen it, the AppleTVs will show up again, but again only for a little while. Has anyone else had this same problem and/or know how to prevent it? Thanks for your help.