Me too
I tried modifying the sitemap.xml with <doc> tags and I atleast didnt get the error, but I didnt have any urls either, in fact just a blank screen with <doc />, which makes me assume the sitemap.php is generating top level tags???
The debug shows all big list of notices on the post.php file, but no errors.
When I initially ran the build, I had my sitemap.xml and zip in the sitemap directory, not the blog root. Didnt see they were supposed to go to the root until looking at FAQ, a little late… think that has anything to do with the errors?
Should I delete everything and try reinstalling?