I use an old program favoritesync.exe to manage Windows Favorites across multiple PCs. It creates an xml with the Favorites data and an xsl file to render it. It has been working successfully through IE7. Now I've begun using Firefox (3.5 beta 4) and I get the message "Error loading stylesheet: Parsing an XSLT stylesheet failed." when I try to browse to the xml file.

I've attached are the files involved. How do I determine what the error is?

You can observe this online at http://www.desotonet.com/favorites/index.xml

Well, both are well formed XML documents. You probably should file a bug with the FF folks.