This is an old thread but the same symptom has come back but based on a new cause. I got the error after installing ASP.NET 5 RC1. I solved the problem by deleting this folder:
Users\{yourusername}\AppData\Local\Microsoft\VisualStudio\14.0\ComponentModelCache
(or %LocalAppData%\Microsoft\VisualStudio\14.0\ComponentModelCache), and afterwards restarted Visual Studio.