Added Information
After reading some other similar posts, I should point out that these errors are not category related. I don't actualy use 'posts' on my site - just 'pages'.
the 404 errors are on the following:
feed/
comments/feed/
hello-world/
category/uncategorized/
author/admin/
hello-world/feed/
2012/11/
a
contact-window-cleaning-quote/
Thanks
Paul