After doing enough digging, I finally figured out what was causing my RSS 404; unfortunately, the factors are so random that I can't find any solutions online, and none of the "fixes" for RSS 404s I have found work for me.

I have WP installed at http://www.focalmatter.com/blah but with the blog location set to http://www.focalmatter.com. That bit works.

I also have descriptive permalinks turned on. Those also work.

However, the combination of the two causes my feed RSS not to work. Instead, I get a Page Not Found at the supposed RSS location of http://focalmatter.com/blah/?feed=rss2. It's worth noting that going to http://focalmatter.com/?feed=rss2 also results in a 404 (an actual 404, at that).

If I switch my permalinks to being postid-based instead of descriptive, OR if I keep my blog in the same folder as my WP install, the RSS feed works fine. But the combination of the two seems to break it.

I have a vague idea of why this perfect storm of settings might be breaking the RSS but no clue how to fix it. Any thoughts?

Thanks in advance for any help you can offer.

Forgive the bump, but I've exhausted every self-help avenue I can think of and could really use input from other people.

One more shameless bump before I give up. None of the fixes I find seem to work, and I have no clue how to solve this. You'd think I wouldn't be the only person out there who has both descriptive permalinks and different directories for the install and blog, yet I appear to be the only one with RSS problems.

Sorted it. It was a theme issue, which was why none of the fixes worked.

Would you mind sharing what the theme's issue was? I am having the EXACT issue as you, and have also exhausted every effort I can possibly find.