If you take a look at your stylesheet whether it’s for a blog or a normal website (usually found at domain.com/sitemap.xml), does it throw up the following error: An XSLT stylesheet does not have an XML mimetype? If so what you need to do is put a .htaccess file in the root of your server (if you don’t already have one) and add the following to the bottom:
AddType text/xsl .xsl
What this basically does is make your server read those sort of files (.xsl) and therefore won’t throw any error up. After you’ve done that submit the sitemap to Google Webmaster Tools.