Commented Issue: Custom tool error: Unable to load one or more of the requested types. [96]

I'm getting the following error in VS when I save my cshtml helpers. The generated file is deleted also.
```
Error 2 Custom tool error: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.

```

I've recently moved to VS2012, and this is the first time I have edited my helpers since. Any ideas?
Comments: Found problem source: HostManager.IsMvcProject: if (content.IndexOf("System.Web.Razor, Version=2.0.0.0", StringComparison.OrdinalIgnoreCase) != -1) I don't have reference to System.Web.Razor assembly. I think we should check System.Web.Mvc assembly version too if System.Web.Razor reference not found. As a workaround I added reference to System.Web.Razor assembly