RSS Feed problem — adding blogname after /feed/

Validator says this is fine. The website is http://www.thesocialmarketingdiva.com

When I click on ‘posts’ to get the feed, the link
http://www.thesocialmarketingdiva.com/feed/thesocialmarketingdiva comes up with an error ‘what you are looking for is not there’

How do I get this changed so that the url ends with /feed/ — it worked before I added a bunch of contact form plugins — I’ve since deactivated all plugins and upgraded to 2.9 wordpress (this was happening on 2.8.6). Problem started about a week or so ago — it’s theme independent.