You are right the validates. But this particular feed does not contain podcast episodes and no iTunes elements. It looks like podPress has been deactivated or something else (an other plugin) is preventing podPress from doing its job. On the other hand this feed exists. Which it would not if podPress would be deactivated.
Is podPress active?
Did you install new plugins or plugin upgrades (besides the podPress upgrade)?
Did you change settings of theme or plugins?
But iTunes STILL won't read it.
The iTunes server looks only once every 24h for updates which explains why updates in your RSS feed are not be visible on the iTunes page of the podcast immediately.
Due to the missing podcast elements, iTunes can not find new material. That is probably also the reason why your iTunes page looks a little bit empty at the moment.
The main question is: why are there no podcast element in this podcast feed?
Because there is no setting in podPress which would have such an effect, I suspect that a different plugin (or a theme function) interferes with podPress. That is why I'm interested to know whether you updated other plugins too.