Q: RSS Feed Stopped Working in iTunes (Invalid Enclosure)

Hello,

I have been doing a podcast for 18 months without issue; I set-up an RSS Feed via Feedburner and then followed the same process for adding the content to my blog, which was always the same (create new post, type in description, add an embedded youtube link, and then host the mp3 file directly from the page to be picked up).

A month ago I posted the most recent episode (#22) and it showed up fine; however, I recently added episode #23 and when I checked my podcast subscription a few days later it still didn't show the new episode #23. Additionally, it no longer showed episode #22 or episode #18!!! I changed nothing on the page/feed so I don't see how it would remove old/un-updated podcasts from iTunes that had already been successfully displayed there, and I don't understand why it isn't pulling the newest one into iTunes either.

Here is my podcast info:

website - www.materialdevolution.com

feed - http://materialdevolution.com/feed/

feedburner - http://feeds.feedburner.com/materialdevolution/feeed

When I check an online RSS validator (http://castfeedvalidator.com/?url=http://materialdevolution.com/feed/) it shows that episodes 18, 22, and 23 have an "Enclosure Error":

Enclosure Info:

Invalid Enclosure

I really don't understand what the heck is going on here, any help to answer these questions and get my feed working would be greatly appreciated -

-What is an "enclosure error" and how can it be resolved? (sorry for being a noob)

-Why did iTunes successfully post podcasts #18 and #22 and then remove them later?

-Why does my Feedburner Feed correctly show all 23 Podcasts if there is an issue?

-Does this mean the problem is with how iTunes is seeing these recent podcasts and not with the actual feed?

Thanks so much everyone for the time and assistance.

Best Regards,

Devin