As much as I understand computers and syntax and HTML and XML and all this, for some reason I just COULD NOT get the XML to validate, even when using the examples on feedvalidator.org.
So instead I looked at a program called Feeder for Mac OS X. Not only did it create valid XML, it showed me two minor issues with the feed. The app is great. It has 2 minor bugs which I reported to the author.
There shouldn't be any more problems with the feed now.