(if ntm is reading - you're doing a great job troubleshooting in these forums :-))
My WP feed is located at http://somesite.de/podcasts/customer/de/feed/
In podPress, I have set "Podcast Feed URL" to the same exact URL.
In the feed, the <atom:link> field also shows this URL, as expected.
But the <link> field in the feed leaves out the last subfolder, only showing "http://somesite.de/podcasts/customer/de/"
I have WordPress 3.5.1 running with podPress 8.8.10 installed (I know it's not the latest version, want to avoid update if possible).