title: ExtJS 4: "c is not a constructor"
body: <p>I'm using chrome to develop an ExtJS application.
  Today I tried to open my app in Firefox 10.0.2 and it doesn't even start up.</p>
  
  <p>I keep getting this Error Message:</p>
  
  <pre><code>c is not a constructor | ext-debug.js (Line 6662)
  </code></pre>
  
  <p>I'm not sure where to start to get rid of this issue.</p>