When I open Visual Studio everything is fine, but when I open any solution, it comes up with an error:
Visual Studio 2012 for Windows Desktop has stop
I had exactly the same problem, additionally I could not create new projects because of "no exports were found that match the constraint contract name" error. I made a small research and the answer from this question helped me to resolve both issues. Now I can create and open my previous projects. What I did is to delete this folder:
%AppData%\..\Local\Microsoft\VisualStudio\11.0\ComponentModelCache