Looks like MSVS 11.0 Beta spoiled a MSVS 10.0 installation

Question

I ran into compilation problems with my MSVS 10 after installing MSVS 11Beta. Now, when I compile my C# Projects in MSVS 10 (Projects created in MSVS 10; Target framework: 3.5),

Answer 1

Another possible fix is to change the target framework of your projects to .Net 4.0. It's not always a solution, but it certainly is a possibility if all else fails.

Answer 2

Setting Setting DisableOutOfProcTaskHost = true in an environment variable worked for me.