I recently purchased a new desktop. The ITUNES was loaded on the new desktop. When I open ITUNES I continually receive a message about ITUNES can't be backed up -50 unknown error. The music is there however it will not update times and date played and the annoying message continually pops up after closing. Also it skips some songs and when I try to play it asks me to sign into the store and when I do and authorize the song I receive the message this song is already authorized for this computer you have used 4 of 5 authrizations. Yet is still will not play. This seems to be a loop as the exact same process happens for several songs. Still listed in Library just will not play.