By default Joomla's RSS feeds do not provide an absolute URL to the content item which leaves the RSS looking like the following:
<link>some_piece_of_content.html</link>
This is okay when the RSS source is the host website but if you are running the feed through FeedBurner some feed readers (and Technorati) can get confused. When they get confused the resulting URL to the source item becomes:
http://feeds.feedburner.com/some_piece_of_content.html
Which of course does not work. To fix this edit the /components/com_rss/rss.php file in the Joomla installation directory. Find the line that reads:
$item_link = sefRelToAbs( $item_link );
And add the following below it:
$item_link = htmlspecialchars( $mosConfig_live_site ). $item_link;
This will generate complete URL's for your RSS readers and solve any inconsistancies with the feed readers out there.