When I announced my new blog engine, the RSS rendering was not finished yet. In fact, the URL that used to hold it, presented the HTML rendering.
For all aggregators, the RSS feed is working again, like before.
I also discovered that my new blog engine uses month numbers in stead of abbreviated month names in the permalinks. That caused old links to the archive to fail. I now accept both month names and numbers, but still produce only the numbers. I think I like it better and it is (because of the order) unambiguous.