@George tl;dr Thanks, you just saved me a few hours of head-scratching.
Yup, that was it. http://site.com/boo to http://site.com/yeah and put a redirect in boo. But I didn't update the apache config to allow yeah to use .htaccess (since allowing .htaccess is off by default) like boo. This was so transparent to me, I had no idea what was going on.