title: The referenced project x does not exists
body: <p>Hej All, 
  I upgraded my solutions of a project from vs2008 to vs2010. </p>
  
  <p>But right now I have a weird problem. I reference a project in multiple solutions (3 solutions)
  In 2 of those solutions the referencing goes wrong. </p>
  
  <p>I am able to add the reference (project reference) but when I build I got the warning the referenced project x does not exists. And errors that I have to add an reference. </p>
  
  <p>I already deleted and added the project again, same with the references but no result.</p>
  
  <p><img src="https://i.stack.imgur.com/0docQ.gif" alt="enter image description here"></p>
  
  <p><img src="https://i.stack.imgur.com/myAZY.gif" alt="enter image description here"></p>
  
  <p>Does anybody have any idea? </p>
  
  <p>Greetz,</p>
  
  <p>Jonathan</p>