title: After upgrading to Rails 3.1.1: "undefined method `javascript_expansions'" error
body: <p>Ive upgraded rails from 3.0.10 to 3.1.1 and now Im getting the following Error:</p>
  
  <p><code>undefined method 'javascript_expansions' for ActionView::Helpers::AssetTagHelper:Module</code> </p>
  
  <p>but not on every page, just some pages are involved. I googled it already but I didnt find anything! Im running ruby 1.9.2 by the way...</p>
  
  <p>Also my asset pipeline doesnt seem to work. Its not loading the <code>application.css</code>and <code>application.js</code> file even its in the <code>assets</code> subfolders. Im getting a routing error each time I try to fetch any of the files.</p>