If you're new, it could be a browser problem or setting. Things are a little slow today, but I'm working fine (including using the one-page and Upload in Images).
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 .