RSS Feeds Valid but Empty

Somehow, over the course of the last couple of days, our feed became completely empty of items. The feed is still valid, but no matter what we try, we can’t get it to repopulate with content. Our site is a podcast network with twelve different feeds that go out to iTunes and the like, so we use BluBrry Powerpress’ category podcasting to separate the main feed by show. Before this happened, I created a php.ini file in wp_admin to increase the upload limit and regenerated the .htaccess file after trying another upload limit increase method that just broke the site. Everything seems to be running fine other than content not appearing in our feeds. We’re frankly mystified as to how this happened, or how it’s even possible. Any insight would be very much appreciated.

Things we’ve tried:

deactivating all plugins
switching back to the default template
re-installing WP 4.0
regenerating the .htaccess file
re-saving the permalinks structure
renaming the feeds/slugs
throwing things against the wall in impotent fury