title: Can't remove Rails under Ubuntu
body: <p>The system returns rails 2.3.5 responding to <code>rails -v</code>. However it returns "rails not installed" for <code>gem uninstall rails</code>.</p>
  
  <p>The system returns error for <code>gem install rails</code>:</p>
  
  <pre><code>@ubuntu:~$ gem install rails
  ERROR:  While executing gem ... (Gem::DependencyError)
      Unable to resolve dependencies: rails requires activesupport (= 3.1.1), actionpack (= 3.1.1), activerecord (= 3.1.1), activeresource (= 3.1.1), actionmailer (= 3.1.1), railties (= 3.1.1), bundler (~&gt; 1.0)
  </code></pre>
  
  <p>Any idea about the problem?</p>