The fix for this error in the Joomla News feed / RSS feed facility in Joomla 1.5 is very simple, but is frustratingly difficult to find. There are many, many forum posts about this, none of which have any answer. (Chmod 777 is NOT a solution.)
The simple solution is this – use this url:
…where “id=1″ is the category id number (find it in Content>Category Manager) of the category you want to use as your rss feed. Or if you change ‘category’ to ‘section’, you can put in the id of the section you want as an rss feed.
That’s it. Plug that in, and it will give you a standard look rss feed. From there, putting in feedburner, or other RSS facilities is easy.
Hope that saved you some time!
P.S. – If you need an atom feed, just replace rss at the end of the url with atom…. Yep. That easy.