If you recently upgraded your iphone or ipod to the new iOS 4.2, then you might be shocked to find all your media is missing. If your videos appear non existent or your music and photos have vanished after running the update there is no need to fear! You are likely suffering from the iOS 4 No Content you can download music from iTunes bug.
A simple fix for this problem is to connect your idevice to your computer and allow iTunes to open.
Next, select the the phone or ipod touch from the list of devices and click “Music”.
Play a song from the library and then re-sync.
Finally, click eject and disconnect your apple touch device from the computer.
Everything should now be back to normal!