Here’s another tip.
This just happened to me the other day. I synced my iPod Classic, went to look at cover flow mode, and half the albums just showed up as pure black.
I did a little searching, found a suggested fix, tried it, and it worked. Here’s what you do if you run into this problem…
Connect the iPod and open iTunes.
Go to the music tab. Uncheck “Display album artwork on your iPod“. The iPod should actually, at this point, automatically sync again. If it doesn’t, just sync it.
Then re-check the box (“Display album artwork on your iPod“), and sync the iPod again.
Worked perfectly for me. Good luck.