When playing certain songs, when I turn on the screen, it'll show the artwork on the screen before I unlock it. On other songs, it just shows my wallpaper. Now the problem is that on these other songs I still have album artwork attached, they just don't show up. They only show up if I go to the actual music player app on the iPod, but not on the 'slide to unlock' screen. I don't understand why it does it for some but not others. Anyone know why?