iTunes copies same songs/artwork every sync

Every time I synced my iPhone 4S iOS6 via USB cable to iTunes 10.7, the same 83 songs or related artwork would sync. Very annoying as the sync would take longer. I figured out the problem. The artwork on all those songs was the culprit. Perhaps it was a defective image. Nevertheless, I deleted all the artwork for those songs and the problem vanished.

The situation frustrated me so hopefully this post will be helpful to others. The songs were part of a collection called "The Rolling Stone Magazines 500 Greatest Songs Of All Time".