I initially had the feed working properly in Firefox by removing the word feed: from the links as per the official fix. After I installed and activated a new theme, the feed error returned. I had forgotten to remove the word "feed:" from the link code in the new theme, and the database obviously becomes fixated and prefers calling up that link, rather than the fixed link. Even after I fixed the new theme (rss link), the error wouldn't go away. I was certain that the new theme was the source of the error because I had the feed working previously with eight different "fixed" themes using the Theme Switcher. Here is what I did to fix it, after correcting the links on the new theme. I activated Kubrick as default theme. Then I deactivated the theme switcher plugin. Then I removed the theme switcher code from the Kubrick sidebar php, and saved the change. I then opened the homepage in my browser and found that the rss link was again working correctly (without the theme switcher). Then I added the theme switcher code back onto the sidebar php. Then I activated the theme switcher plugin. The rss feed was still working correctly. I only did the change to the (one) default theme; I knew the other themes were working correctly previously. I suppose that it might be possible to just deactivate the theme switcher plugin, and then reactivate it. Maybe this re-sets the database. I didn't try that out. But for me, the fix was removing the theme switcher code, then adding the code again. I'm not very tech smart, so if this solution sounds absurd, please remove this post.