We have had our Podcast at iTunes for 5 years and never had an issue with the icon in our feed.
This just noticed this happening this morning.
Our feed is http://feeds.feedburner.com/modtv/podcast
Our ITunes Podcast is http://itunes.apple.com/us/podcast/modtv-fashion-network-podcast/id111082774
We checked our Feedburner settings and noticed that the icon was not showing up so we changed the url for the image to this.
It is still not showing up in iTunes. Perhaps it still needs to update. Any suggestions you can provide would be so appreciated. Thank you so much in advance.