[Plugin: WordPress SEO by Yoast] XML sitemap on Multisite network shows error

WordPress version: 3.3.2 Multisite
WordPress SEO version: 1.1.9

I did this: Network activated sitemap plugin on Multisite, then on a subsite.

I expected the plugin to do this: show the sitemap for the subsite.

Instead it did this:
It cerated the sitemap link but when clicking on the sitemap link, I got:
Error loading stylesheet: An unknown error has occurred (805303f4)

https://www.ads-software.com/extend/plugins/wordpress-seo/