encyclo - 1:15 am on Apr 25, 2006 (gmt 0)

When you use the mime type text/xml you need to explicitly specify the character encoding with an HTTP header rather than just in the XML prolog. Dependent on your setup, you can do this via server-side scripting which is generating the RSS file, or via a .htaccess file for Apache.

AddType text/xml;charset=iso-8859-1 xml

This is because you are delivering the XML file via HTTP, whose character encoding rules take precedence other the charset defined in the document.