I have just created an ASP.NET MVC 4 project and used Visual Studio 2012 RC to create a Controller and Razor Views for Index and Create Actions.
I had the same problem and I used WinMerge to help me track this down. But as I researched it more, I found that Rick has the perfect blog post for it.
Summary:
to both web.config filesInstall-Package -IncludePrerelease Microsoft.AspNet.Web.Optimization