[Plugin: Google XML Sitemaps] Paths don't match

Hi

I have this problem with google webmaster

Paths don’t match
We’ve detected that you submitted your Sitemap using a URL path that doesn’t include the www prefix (for instance, http://example.com/sitemap.xml). However, the URLs listed inside your Sitemap do use the www prefix (for instance, http://www.example.com/myfile.htm).

what should i do?

Thanks

http://wordpress.org/extend/plugins/google-sitemap-generator/