title: invalid gem format
body: <p>Installing Merb on Ruby Enterprise Edition (OS X) throws this error, any ideas?</p>
  
  <pre><code>sudo gem install merb
  
  ERROR:  Error installing merb:
  invalid gem format for /opt/ruby-enterprise-1.8.6-20090113/lib/ruby/gems/1.8/cache/ParseTree-3.0.2.gem
  </code></pre>
  
  <p>Deleted the gem cache but the problem persisted. It seemed to manage to install some of the gems though. </p>