Julia, I'm having the same issue. It will allow me to highlight my display name, but won't let me type in the box, The other fields can be changed, but not that one.
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 .