WordPress Version: 3.4.2
WP Seo Version: 18.104.22.168
Description of the issue:
The sitemap feature did not work, Google's sitemap validator was complaining about an invalid format and Google Chrome's integrated XML Parser was also complaining about illegal characters.
After some investigation I realized that this had to do with the HTTP Status header sent by WordPress SEO. I just removed that line and it worked like it is supposed to. So, if you are experiencing the same issue applying the following patch might help: click.
Why does WP SEO send a status header? Seems to be rather pointless to me.