Here's something strange. I recently added an 8GB external card and copied a few gigs of music to it. When browsing through My Music via All Songs, all the songs are visible and they play fine. However, when browsing via Artists or Albums some of the songs are missing. I tracked it down to being the bit rate of the song. Any song over 192kbps does not show up. For instance, when looking at U2's latest album only the songs ripped at 192kbps or below show up, those at 256 don't. With another album all the songs were ripped at 320kbps. The entire album is not visible.