Windows Phone 8 Application XAML Designer fails to load and intellisense not working

安装Windows Phone 8 SDK，新建一个Windows Phone App，加载XAML设计器失败，同时智能提示无效。但新建一个WPF Application没有问题。设计器错误如下：

System.UnauthorizedAccessException

Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))


at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.WaitForCompletion(NestedCallContext nestedCallContext, BlockingCall call, WaitHandle timeoutSignal)   at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.MarshalOutSynchronous(Action action, Int32 targetApartmentId, WaitHandle aborted, WaitHandle timeoutSignal)   at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.MarshalOut(Action action, Int32 targetApartmentId, WaitHandle aborted, CallSynchronizationMode syncMode, WaitHandle timeoutSignal)   at Microsoft.Expression.DesignHost.Isolation.Remoting.ThreadMarshaler.MarshalOut[TValue](RemoteHandle`1 targetObject, Action action, CallSynchronizationMode syncMode)   at Microsoft.Expression.DesignHost.Isolation.Remoting.ThreadMarshaler.MarshalOut[TResult,TValue](RemoteHandle`1 targetObject, Func`2 func, CallSynchronizationMode syncMode)   at Microsoft.Expression.DesignHost.Isolation.Remoting.LocalDesignerService.CreateDesignerImpl(IHostSourceItem item, IHostTextEditor editor, RemoteCancellationToken remoteCancelToken)   at Microsoft.Expression.DesignHost.Isolation.Remoting.LocalDesignerService.<>c__DisplayClass12.<Microsoft.Expression.DesignHost.IDesignerService.CreateDesigner>b__11(RemoteCancellationToken remoteToken)   at Microsoft.Expression.DesignHost.Isolation.Remoting.LocalDesignerService.CallWithCancellation[TResult](CancellationToken cancelToken, Func`2 func)   at Microsoft.Expression.DesignHost.Isolation.Remoting.LocalDesignerService.Microsoft.Expression.DesignHost.IDesignerService.CreateDesigner(IHostSourceItem item, IHostTextEditor editor, CancellationToken cancelToken)   at Microsoft.Expression.DesignHost.IsolatedDesignerService.IsolatedDesignerView.CreateDesignerViewInfo(CancellationToken cancelToken)

msdn论坛也有不少人出现同样问题，修复或重装Visual Studio 2012都无法解决。其中有一个帖子：http://social.msdn.microsoft.com/Forums/en-US/toolsforwinapps/thread/218cde67-8f17-4db7-9628-aaab4582c561 提到安装Visual Studio 2012 Update 1问题解决。

Visual Studio 2012 Update 1 CTP 4 => http://www.microsoft.com/en-us/download/details.aspx?id=34818