XML sitemap error with latest version 1.4.13

I don’t know why this topic was closed

I just reset to the default Twenty Twelve WP theme and disabled ALL other plugin and cache is cleared. But I still have the error:

Error loading stylesheet: An XSLT stylesheet does not have an XML mimetype:

The error appears in Firefox, empty page when using Chrome or Safari.

My site:

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