That usually happens when a large number try to access the site at the same time. It may have had to do with people trying to check for an update on the body found in the river.
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 .