Hello,

probably Google is right, there is a Joomla redirect to an html page or some plugin that broke th XML output of Joomla.
You can easily test it opening the link in your browser, normally you should get plain XML.

Of course if you have installed sh404sef this can be related to this extension, you need to configure it as reported in the pdf document 'sh404sef configuration for jsitemap'

Contact me at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it if you need on site help.

Greetings

John