Joomla Bible Study

I've recently created a podcast for our sermons and have successfully added it to the iTunes store. The only thing I haven't figured out is how to get our artwork to display within iTunes. It seems to work fine if I go directly to the XML inside a browser. Does it just take some time for Apple to pickup the link? It appears that the XML has the proper link to the image. Any advice would be appreciated.

Website: www.smcoc.net under the Media tab

XML: www.smcoc.net/podcast.xml

I just started creating my podcast files through GarageBand. If I export as an mp3 it does not allow inclusion of the art. If I export in Apples AAC format (m4a) it includes the art.
Hope this helps.