title: Visual Studio 11 - Design view is unavailable for x64 and ARM target platforms because the document contains custom elements
body: <p>I'm test-driving Visual Studio 11 beta and it appears I've hit a major snag.</p>
  
  <p>Has anyone tried opening an actual production WPF project that contains WPF windows with User Controls? When I try to open a WPF Window or control that contains user controls, the design view displays a nice error message: </p>
  
  <blockquote>
    <p>"Design view is unavailable for x64 and ARM target platforms because the document contains custom elements."</p>
  </blockquote>
  
  <p>It appears to be a major wtf... since most developer machines these days are x64. </p>
  
  <p><strong>* UPDATE: *</strong></p>
  
  <p>Reproduced this in a new VS 2011 WPF project:</p>
  
  <ol>
  <li>Add a xaml resourec file with styles (in the same project as the user control)</li>
  <li>Reference this file in a user control using the  tag</li>
  </ol>
  
  <p>Immediately, the "Design view is unavailable for x64 and ARM target platforms..." pops up. </p>
  
  <p>As soon as I remove the resource reference, the designer starts working again. </p>