[Plugin: WordPress SEO by Yoast] Sitemap error WordPress SEO

WordPress SEO version: 1.2.5

I did this: i disabled all plugins and i switched to the default WordPress theme for a bit.

I expected the plugin to do this: the sitemap works normally.

Instead it did this: 404 not Found

my blog adress: http://aquecendoabarriga.com.br

all the best

http://wordpress.org/extend/plugins/wordpress-seo/