The title tag for your episode of 4th November reads:
<title>Obedience- It's the theme of our story & always results in God's Glory!</title>
You cannot have an ampersand ('&') by itself in a feed because it's used in XML to signify the beginning of a code sequence; as there is no closing, the entire rest of the feed is rendered unreadable, and as the final tags are effectively not present this wrecks the entire feed. The Store is showing a cached version of the feed but attempts to subscribe fall over because of this error.
You need to replace the ampersand either with the word 'and' or the code
Gramatically speaking 'and' would be correct - not that it's a technical issue but you shouldn't really use an ampersand in a sentence in this way. However, that's an artistic decision for you: but you must lose the ampersand.
You have the same issue in the title for the episode of 22 July.
For reference, your feed is at
The 'enclosure' tag for 22 July reads:
<enclosure url="http://missionbaptist.com/audio/Sermons/2012/2012.07.22%20Failure%20of%20Man%20&%20Victory%20of%20God.mp3" length="1" type="audio/mpeg" />
has an ampersand which should not be there (I've highlighted it in red - you may need to scroll right to see it). As a general rule you should not have spaced in filenames: spaces are not allowed in a URL. Your feed has correctly substituted the code %20 for each space, but it's really something you should avoid - the usual practice is to replace spacdes with an underscore. Also, the 'length' should be the file size in bytes, not '1'. Nonetheless, it's the ampersand which is now wrecking your feed.
There is a similar issue in the media file URLs for 29 April and 11 October - in this case it may not wreck the feed as it is the @amp; code but it shouldn't be in a URL. it may be that the original URL does contain an ampersand, but if dealing with the first error above doesn't solve the problem you should look into changing these.