I don't know how long it has been broken, but I saw my Google rankings drop and decided to do some research.
I found that all of my categories would return 404's and my sitemap was generating 404s in Google Webmaster Tools.
I began deactivating plugins and was surprised to see the 404 category taxonomy issue disappear once I deactivated WordPress SEO (this plugin has been rock-solid which is why I was surprised).
XML Sitemap Issues
I was running 1.14.13 when these issues were discovered, and was excited to see 1.14.14 come out right in the middle of the issues. I immediately updated. It appears the Category 404s went away, but I now get this instead when I try to go to the sitemap:
Error loading stylesheet: A network error occurred loading an XSLT stylesheet:http://example.com/sitemap.xsl
I've tried all of the fixes suggested including updating my .htaccess according to Yoast.com as well as disabling sitemaps and re-enabling, but no matter what, I always get the error.
For now, I'm considering turning off sitemaps and using google XML sitemaps or ditching WordPress SEO altogether and just using Genesis SEO with Google XML sitemaps.
I love WordPress SEO, so I hope these are just some hiccups, but I was definitely bummed to see my Google ranks slip. That costs money :-/
Anyways, I'm not trying to be a freeloading complainer. You guys are awesome, and I hope this works out (and honestly, I'd pay for a premium version of this plugin sans-these issues), but I wanted to let you know what I was experiencing as your customer (albeit a freeloading one).