Google: 'Your Sitemap appears to be an HTML page.'

Hi,

I disabled page cache on this plugin as well as most other things it has to be said and I’m still having issues. This time with the XML file. Google can’t see it and when I try to look at it myself all I get is a blank page that takes less than a second to load.

Any help?

http://wordpress.org/extend/plugins/w3-total-cache/