Symptoms
Upgraded to Visual Studio 2013 and can't open Visual Studio 2012 K2 workflows.
Diagnoses
Permissions on the VS 2013 folder were not given so when upgrading to 2013, the required dlls were not added. Added "Everyone" permissions on the folder, then was able to copy over the dll files from the 2012 VS folder to the 2013 VS folder.
Resolution
Adding the dll files over from 2012 Visual Studio to 2013 Visual Studio folder and providing permissions on the folder allowed 2012 Visual Studio workflows to be visible in 2013 Visual Studio.
