I have had iTunes for a long time, and used it with no problems, syncing with two iPods and an iPhone. The other day, however, after syncing with an iPod, my entire library had exclamation marks next to each song and when I click them, or try to play a song, I get the message "The song "______" could not be used because the original file could not be found. Would you like to locate it?" I cannot locate the songs or understand what happened. My iPod plays the songs but the iMac doesn't play them from iTunes. Any help is appreciated. I have an iMac and the latest version of iTunes.