InvalidCastException is thrown after installing ASP.NET MVC 4 Beta

I had the same problem, but when migrating ASP.NET MVC 3 to ASP.NET MVC 4. This way I got on this topic.
I have found a solution to the problem, but its source is different, it is not from WebPages version.

I have followed the official guide (so to say) Upgrading an ASP.NET MVC 3 Project to ASP.NET MVC 4.

To resolve the problem, you have to add in Web.Config (probably around previously added ones):

<runtime><!-- Should be there by default, near end -->
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><!-- Should be there by default -->
    <dependentAssembly>..</dependentAssembly><!-- Should be there by default -->
        ... some other dependecy redirects ...

    <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages.Razor"
            publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0"/>
    </dependentAssembly>

        ... some other dependency redirects ...
    </assemblyBinding>
</runtime>

Also in the notes is not mentioned to change the Reference of System.Web.Helpers from 1.0.0.0 to 2.0.0.0 (delete and add the new one).