Hello! If you haven't already done so, you can view the CSV Upload FAQ and see if your answer is there. Otherwise I'd recommend you file a Customer Support Request and let them know about the error messages you have been receiving.
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 .