Well thanks to Sean Corfield I understand why I was having issues with namespaces when trying to parse RSS 1.0 with XPath.
If you have a document with namespaces such as RSS 1.0, you need to fully qualify name spaces in your XPath queries, such as: /rdf:RDF/ - that makes sense, but what I didn't realize is that you still need to qualify the namespaces, when namespaces are used in the document for elements using the default namespace, such as item: /rdf:RDF/:item/.