title: "Unspecified error" trying to open VS2010 solution in VS2012
body: <p>I have a Visual Studio 2010 .sln file which I would like to convert to Visual Studio 2012. While this task should be fairly simple following for example <a href="https://stackoverflow.com/a/12406912/3242721">this SO answer</a>:</p>
  
  <blockquote>
    <p>I managed to 'convert' the solution file to change the line containing '# Visual Studio 2010' to '# Visual Studio 2012' in the .SLN file.</p>
  </blockquote>
  
  <p>it started to produce "Unspecified error" every time I try to open such upgraded solution in Visual Studio 2012.</p>