title: Problem with preview in Sitecore 6.2?
body: <p>When i try to preview a page in my Sitecore solution, i get this asp.net error;</p>
  
  <pre><code>The Controls collection cannot be modified because the control contains code blocks (i.e. &lt;% ... %&gt;). 
  </code></pre>
  
  <p>What could be causing this - it is only showing in preview mode, any other works fine?</p>