You should open up a support case, and we'll be able to look into this issue for you. Click on the "Help" link, and in the third box down on the right side of the page, there's a link to file a support request.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .