RSS feed has XML Parsing Error, invalid but appears fine in Safari

The RSS feed for ccky.org is https://ccky.org/feed/. I’m able to subscribe to this feed with no problems via Google Reader and I can read it fine in Safari, but when I try to access it directly in Firefox, I get this message

XML Parsing Error: XML or text declaration not at start of entity
Location: https://ccky.org/feed/
Line Number 3, Column 1:<?xml version=”1.0″ encoding=”UTF-8″?>
^

When I try to burn a Feedburner feed using it, I get this message

The URL does not appear to reference a valid XML file. We encountered the following problem: Error on line 3: The processing instruction target matching “[xX][mM][lL]” is not allowed.

And checking the feed’s validity yields these messagesL

This feed does not validate.

line 1, column 1: Blank line before XML declaration [help]

^

In addition, interoperability with the widest range of feed readers could be improved by implementing the following recommendation.

line 38, column 0: content:encoded should not contain iframe tag (5 occurrences) [help]

Any idea how I can fix this problem? Thanks!