title: How to get rails server to start?
body: <p>I can't get me rails server to start.</p>
  
  <p>I am on a mac, using a clean install of <a href="https://github.com/fortuity/rails3-mongoid-devise" rel="nofollow">rails3-mongoid-devise</a>, Rails 3.0.5 and Ruby 1.8.7 patch level 174.</p>
  
  <p>When I try try to start the rails server I get the following message and it never starts.</p>
  
  <pre><code>MBP:test-ror stephen$ rails s
  =&gt; Booting WEBrick
  =&gt; Rails 3.0.5 application starting in development on http://0.0.0.0:3000
  =&gt; Call with -d to detach
  =&gt; Ctrl-C to shutdown server
  Exiting
  /Users/Sites/workspace/test-ror/config/environment.rb:4: uninitialized constant YAML::ENGINE (NameError)
      from /Users/Sites/workspace/test-ror/config.ru:3
      from /Library/Ruby/Gems/1.8/gems/rack-1.2.2/lib/rack/builder.rb:46:in `instance_eval'
      from /Library/Ruby/Gems/1.8/gems/rack-1.2.2/lib/rack/builder.rb:46:in `initialize'
      from /Users/stephen/Sites/workspace/atrack-ror/config.ru:1:in `new'
      from /Users/Sites/workspace/test-ror/config.ru:1
  Stevos-MBP:atrack-ror stephen$ 
  </code></pre>