title: Running VMC on Mountain Lion
body: <p>I've followed the simple instructions for installing VMC on Mountain Lion (<code>sudo gem install vmc</code>), but I'm getting the following error:</p>
  
  <pre><code>$ vmc
  /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems.rb:230:in `activate': can't activate multi_json (~&gt; 1.4.0, runtime) for ["vmc-0.4.7"], already activated multi_json-1.5.0 for ["cfoundry-0.4.19", "vmc-0.4.7"] (Gem::LoadError)
      from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems.rb:246:in `activate'
      from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems.rb:245:in `each'
      from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems.rb:245:in `activate'
      from /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems.rb:1056:in `gem'
      from /usr/bin/vmc:18
  </code></pre>
  
  <p>Can anyone help me with diagnosing this?  Is this an issue with the version of Ruby installed?  I don't really want to blindly jump through hoops to upgrade Ruby for this one thing. I tried installing an older version of multi-json with <code>gem install multi_json -v 1.4.0</code>, but this didn't seem to make any difference.</p>