I realize those versions are extremely old, but the last day or so I have been working with Wicked Edge‘s Web admin with fixing the RSS feed from their site. Mail and Outlook both saw everything fine, but the W3C RSS validator knew it was broken, and Google Reader would produce very odd results, mainly by reading the content, but the URLs would be incorrect.
The issue boiled down to Joomla 1.5.20 not encoding ampersands in the RSS section. So instead of:
http://www.wickededgeusa.com/index.php?option=com_kunena&func=view&catid=3&id=5979&Itemid=63
You’d get (note the missing &’s):
http://www.wickededgeusa.com/index.php?option=com_kunenafunc=viewcatid=3id=5979Itemid=63