I am having problems with Google webmaster tools and sitemaps with my domain.
When setting the sitemap all I get from webmaster tool still is -->Sitemap is HTML ... and I think I found out the reason:
I registered on google webmaster tools my site as http://mydomain.com but the app is hosted on appspot at http://myapp.appspot.com which is mapped to mydomain.com.
If I register http://myapp.appspot.com everything works fine (sitemap validated) - so it looks the problem is somehow related to the fact that http://myapp.appspot.com is mapped to http://mydomain.com.
This it's not ideal because I need a sitemap for mydomain.com ... any idea about how to overcome?
Check to make sure the links in your sitemap are pointing to mydomain.com not myapp.appspot.com.