Seems to be another bug in iTunes - you now can't update the artwork to anything you've added yourself if your iTunes library exists on external/NAS storage. (it does work OK if your library is locally stored - i tested that). This program has to be the most clunky anal sucking piece of code ever released by anyone. I don't recall the last time it was working - looks like Nov based on my files dates. Anyone know if was an Mavericks or iTunes update that broke this?