[Plugin: WordPress SEO by Yoast] Incredibly slow sitemap – bug?

Hello,

Here is my sitemap: http://marzycielskapoczta.pl/sitemap_index.xml

It takes around 3 minutes to load page-sitemap (I have ~200 pages) and it’s impossible to load post-sitemap (Google can’t access it either).

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