I'm having a slightly different problem with my sitemap.
My category-sitemap.xml is 404-ing.
I have disabled 'Strip Category Base' and 'Enfore trailing slash' until the obvious bug is solved.
However, my category-sitemap.xml still leads to a 404.
I have tried enabling and disabling sitemaps, but nothing seems to change. I've tried updating my category sitemap, but again, it still 404s.
My website is visible at http://ryancaseybooks.com if that helps in any way.
Apparently Yoast is away on holiday unitl August 6th according to Twitter. I apologise to him for all our concerns - the last thing we want to do is ruin your holiday Yoast!
Although, if the problem isn't resolved quickly, I can see a lot of people leaving WordPress SEO as a kneejerk reaction. I really don't want to have to do that. I love the plugin.