[Plugin: Google XML Sitemaps] Error loading stylesheet:

I keep getting this error.

Error loading stylesheet: An XSLT stylesheet does not have an XML mimetype:http://www.motorthusiast.com/wp-content/plugins/google-sitemap-generator/sitemap.xsl

http://www.motorthusiast.com/sitemap.xml

Any idea why?

http://ww.wp.xz.cn/extend/plugins/google-sitemap-generator/