Feedburner stopped working, URL does not appear to reference a valid XML file?

I have been using feedburner for nearly two years and when recently checking on my feed I discovered that it had lost all formatting and the page now looks like this (http://feeds.feedburner.com/Cape27Blog).

I logged into my feedburner account and saw this message:
The URL does not appear to reference a valid XML file. We encountered the following problem: Error on line 5: The processing instruction target matching “[xX][mM][lL]” is not allowed.

I’ve recently had a new design installed on my site. Could this be the source? Not too familiar with XML. Please help. Completely out of ideas.. Thank you!