Just wondering if this has happened to anyone else: I started to add some artwork (album covers) to my songs in iPod. Just thought it'd be nice to see them in the info when I have my iPod docked to the PC. After I started to do this to my song files, my smart playlists on my iPod would show up empty. I could see the playlist songs only in iTunes.
Only after I purged all the artwork from my song files, did the smart playlists start to show the songs. I guess the image file info was a bit much for the iPod to process.