All of the songs I've downloaded via iTunes are showing in the music library on my 5th Gen iPod Touch, but anything I've added to iTunes via my computer isn't available.

All of the songs I've downloaded via iTunes are showing in the music library on my 5th Gen iPod Touch, but anything I've added to iTunes via my computer isn't available. The songs all have a red circle with a red square in the middle and if I select one, the iPod rapidly changes from that song to the next, to the next until it has gone through all of the songs on that particular album. Everything is still in my iTunes library, but the iPod somehow doesn't recognize the songs. I just performed the iOS 7.0.6 update on Sunday and my iPod worked fine before...is the update somehow messing up the music on my iPod?