Feed suddenly not updating in feedburner and getting resync errors

The feed on my WP blog is suddenly not working – it will not update and show my most recent post. (http://www.trans-americas.com/blog) and I have tried everything I can think of. I have not made any updates to the blog since it was last working at the end of last week,

– My source feed http://trans-americas.com/blog/feed/ shows the most recent post (“Sloths in the City”) but my feedburner feed does not http://feeds.feedburner.com/Trans-AmericasJourney.

– Both my original feed validity http://feedvalidator.org/check.cgi?url=http%3A%2F%2Ftrans-Americas.com%2Fblog%2Ffeed%2F, and my feedburner feed validity http://feedvalidator.org/check.cgi?url=http%3a%2f%2ffeeds.feedburner.com%2fTrans-AmericasJourney appear to be fine. However, the original shows the most recent post but the feedburner does not.

– When I ping my original feed I receive the following error
Your Ping resulted in an Error “We were unable to process your ping. You must ping with a URL that exactly matches the channel link (RSS) or alternate link (Atom) in your top level feed element pointing back to your website (e.g http://myblog.blogspot.com/), or use your feed URL (e.g. http://feeds.feedburner.com/myuri).”

– When I ping my feedberner feed I receive a message that it was successful, however it does not update the new post.

– When I resync the feed I receive the following message:
“There is an issue that must be addressed with your source feed for the feed “Trans-Americas Journey Blog”

– I have deactivated all plugins and that does not solve the issue.

Any ideas as to what can be causing this.
Thanks