title: Rails 3.1 on Ubuntu 11.04 via RVM - uninitialized constant Psych::Syck
body: <pre><code>gem install rails --pre
  ERROR:  While executing gem ... (NameError)
      uninitialized constant Psych::Syck
  </code></pre>
  
  <p>I can't seem to find any info on how to resolve this. Has anyone else had the same problem?</p>
  
  <p>I am using a newly created gemset in RVM with Ruby 1.9.2</p>