Please file a support case about this issue from under the "Help" tab within your account and we will look into this for you. I am not aware of any current technical issues that would explain the behavior you described.
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 .