ipod won't play certain songs but they play on itunes

I have an 80gb ipod classic and recently it has stopped playing certain songs in an album. It just skips ahead until it finds one it will pay. I've done a reset and restore but still the problem persists. Yet itunes will play all songs and gives no indication of a problem. It doesn't matter where the songs came from or how old they are (as in when put on itunes).