Support screen, or apple logo?

What causes the iPod video to go to the support screen or the apple logo and not go any farther, and what can be done to fix it? also what could be wrong if everything works but the iPod won't play? the screen works, the click wheel works, you can download songs, but they won't play, and if you open itunes and go to the library on the device it shows all the songs but the list is greyed out? i restored it through itunes and held the menu and center button and the menu and play button, but nothing helped. thanks.