I have made that dreadful error of upgrading from MVC4 to MVC5 pre-release by updating the razor, and mvc webpage in my references I have System.Web.Mvc, System.Web.Webpages, System.Web.Webpages.Razor and System.Web.Razor as version v4.0.30319, when I run my application I get

[A]System.Web.WebPages.Razor.Configuration.HostSection cannot be cast to 
[B]System.Web.WebPages.Razor.Configuration.HostSection.

Type A originates from 
'System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location
'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll'.

Type B originates from
'System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, 
PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 
'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\membership\c70f06fe\9163b1ca\assembly\dl3\291c956e\73c25daa_cf74ce01\System.Web.WebPages.Razor.dll'.

is this the same as http://www.asp.net/whitepapers/mvc4-release-notes

Thanks

Adding a stacktrace:

[InvalidCastException: [A]System.Web.WebPages.Razor.Configuration.HostSection cannot be      cast to [B]System.Web.WebPages.Razor.Configuration.HostSection. 
Type A originates from 'System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 
 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll'. Type B originates from 'System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location

'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\c70f06fe\9163b1ca\assembly\dl3\291c956e\73c25daa_cf74ce01\System.Web.WebPages.Razor.dll'.]
System.Web.WebPages.Razor.WebRazorHostFactory.CreateHostFromConfig(String virtualPath, String physicalPath) +193
System.Web.WebPages.Razor.RazorBuildProvider.GetHostFromConfig() +51
System.Web.WebPages.Razor.RazorBuildProvider.CreateHost() +24
System.Web.WebPages.Razor.RazorBuildProvider.get_Host() +34
System.Web.WebPages.Razor.RazorBuildProvider.EnsureGeneratedCode() +85
System.Web.WebPages.Razor.RazorBuildProvider.get_CodeCompilerType() +34
System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider) +189
System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders() +265
System.Web.Compilation.BuildProvidersCompiler.PerformBuild() +21
System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath) +580
System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate) +571
System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate) +203
System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean throwIfNotFound) +249
System.Web.Compilation.BuildManager.GetCompiledType(VirtualPath virtualPath) +17
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +90
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +380
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +109
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +890
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +97
System.Web.Mvc.Async.<>c__DisplayClass1e.<BeginInvokeAction>b__1b(IAsyncResult asyncResult) +241
System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +29
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +111
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +53
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +19
System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__4(IAsyncResult asyncResult, ProcessRequestState innerState) +51
System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +111
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +606
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +288