You are correct. Libsyn, our provider, has "upgraded" their services, and in the process, our RSS feed is no more. I haven't been able to resolve this alone, so I'm waiting for them to answer my plea for help. Since yesterday, it has gotten even worse. Now you can't even direct download Episode 152!
At least iTunes will take the new feed, but you'll have to subscribe as if it is a new podcast (Advanced:Subscribe to podcast) to this. This won't fix the directory in iTunes which still links to the old feed. Now I need to figure out how to update the iTunes directory before they de-list me. UPDATE: The iTunes directory seems to be working now. Now I need to figure out why the RSS widget on the Ning homepage doesn't work.
The rss 2.0 link on the retromaccast.three.libsyn.com page is bad too. Whatever stats you had are completely blown and you've got users that aren't going to know what's happened. I've resubscribed directly to the link you gave and got all episodes so I'm kinda fixed up but that doesn't fix everyone.
Fortunately my stats have been preserved. Yes, it is a pain that everyone will have to switch to the new feed, but other than that we're back in business. I still have no idea why the RSS widget doesn't work.