Your iTunes Store page is at http://itunes.apple.com/gb/podcast/shulamite-podcast/id209503372
Your feed is at http://feeds.feedburner.com/ShulamitePodcast
It all works fine on a Mac: I don't have an iOS device so I'm afraid I can't comment there, except that you're not the first in recent weeks to complain of the same thing, so something odd may be going on.
There are two minor errors in the feed, though I wouldn't have expected them to cause this problem: you have no 'itunes:duration' tags which should carry the duration of each episode, and within the 'enclosure' tags the 'length' attribute is empty - it should show the file size in bytes.
You could ask in the iPhone or iPad forums as appropriate, where someone may be able at least to check whether the problem arises for them.
I figured it out!!
When transfring your podcast from Garageband using the share with iTunes share option you can't select an audio setting higher than an Music Podcast. Higher qualities fail to load the plug in giving you the error.I don't know how that got changed in the settings but that was it.
Thank you, hope this helps others with same issue.