title: "Request is not available in this context" on Masterpage Page's design mode
body: <p>I'm using VS.net 2010 ASP.net C# 4.0 and I've got many pages who use the same Masterpage. But for some reasons I didn't find for now, some pages never display in design mode of Visual Studio. Instead of seeing my designed page, I only see a Gray Square where we can read   </p>
  
  <p><strong>Error creating control - ContentPlaceHolder1</strong><br>
  Request is not available in this context.  </p>
  
  <p>Anyone know a reason and/or a way to resolve this?<br>
  Must tell that there's no errors in my whole solution and I can start debbuging normaly.</p>
  
  <p>Note : I usualy talk french so feel free to tell me if there's something that wasn't clear!</p>