Doesn't Work. Any ideas?

Here's my problem.

I have several podcast listed in the iTunes store, and have just changed the way the RSS feed is created. I'm now using PodPress to create one big feed of every show, and several individual show feeds.

Normally the process of changing the URL of a podcast listed on iTunes involves adding the following line of code to your RSS feed:

<itunes:new-feed-url>new feed url</itunes:new-feed-url>

I've done that several times in the past and it always worked quickly. Unfortunately as soon as I added that code for my new URLs, the feed failed to validate, and iTunes fails to even see the feed at all. So far the only lead that I have is that the new RSS URL is "http://www.mywebsite.com/?feed=rss2&cat20" If I use the URL without the "=rss2&cat20" part then it works fine. Something about that extra bit at the end is screwing up iTunes.

Here's the kicker. If I submit http://www.mysite.com/?feed=rss2&cat20 directly to the iTunes store as a new podcast, it works with absolutely no problems. The sore recognizes the feed, the feed even validates perfectly on feedvalidator.org. It just won't let me swap to the new feed URL in the usual way.

I'm at a total loss as what to do. I don't want to submit all the shows again because we'll end up losing a lot of listeners and causing a lot of work for whoever makes our featured provider page. Any ideas anyone?