I am working on Simply Rails 2. This problem occurs around page 346

I have several stories Story.find(first) returns
Code:
#<Story id: 1, name: "Ogg invades", link: "http://climatecalm.org", created_at: "2009-07-18 10:44:51", updated_at: "2009-07-28 17:09:33", user_id: 1, votes_count: 3>
This is an extract from show.html.erb
Code:
<h2>
  <span id="vote_score">
    Score: <%= @story.votes_count %>
  </span>
  <%= @story.name %>
</h2>
It gives the error:
You have a nil object when you didn't expect it!
The error occurred while evaluating nil.votes_count

This page was working. Does anybody know what's happening?