title: Missing a using directive or an assembly reference error when I'm not missing anything
body: <p>I have a solution with 4 projects. In the first one I reference the other three, not with Browse, but with Add reference->Project tab.</p>
  
  <p>I have all three using statements in the beginning.</p>
  
  <p>The program works fine. I tested it and it works. But I'm not able to build it.</p>
  
  <p>I get the error "Missing a using directive or an assembly reference".</p>
  
  <p>None of my projects are on client profile. (I think .Net 2.0 doesn't even have client profile).</p>
  
  <p>Why is VS doing this? How to resolve it?</p>