System.NullReferenceException Referencia a objeto no establecida como instancia de un objeto

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

System.NullReferenceException
Referencia a objeto no establecida como instancia de un objeto.

Server stack trace:
en Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.WaitForCompletion(NestedCallContext nestedCallContext, BlockingCall call, WaitHandle timeoutSignal)
en Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.MarshalIn(Action action, Int32 targetApartmentId)
en Microsoft.Expression.DesignHost.Isolation.Remoting.ThreadMarshaler.MarshalIn(IRemoteObject targetObject, Action action)
en Microsoft.Expression.DesignHost.Isolation.Remoting.ThreadMarshaler.MarshalIn[TResult](IRemoteObject targetObject, Func`1 func)
en Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteDesignerService.Microsoft.Expression.DesignHost.Isolation.Remoting.IRemoteDesignerService.CreateDesigner(IRemoteHostSourceItem remoteItem, IRemoteHostTextEditor remoteEditor, IRemoteCancellationToken remoteToken)
en System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)
en System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg)

Exception rethrown at [0]:
en System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
en System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
en Microsoft.Expression.DesignHost.Isolation.Remoting.IRemoteDesignerService.CreateDesigner(IRemoteHostSourceItem remoteItem, IRemoteHostTextEditor remoteEditor, IRemoteCancellationToken cancelToken)
en Microsoft.Expression.DesignHost.Isolation.Remoting.LocalDesignerService.<>c__DisplayClass8.b__6(IRemoteDesignerService d)
en Microsoft.Expression.DesignHost.Isolation.Remoting.ThreadMarshaler.<>c__DisplayClass4`2.b__3()
en Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.Call.InvokeWorker()

System.NullReferenceException
Referencia a objeto no establecida como instancia de un objeto.
en Microsoft.Expression.Platform.PlatformService.PlatformEntry.get_PlatformCreator()
en Microsoft.Expression.Platform.PlatformService.GetPlatformCreator(String frameworkSpec)
en Microsoft.Expression.Platform.PlatformService.IsCompatibleFramework(FrameworkName hostFramework, FrameworkName guestFramework)
en Microsoft.Expression.DesignSurface.Project.ProjectContextManager.GetProjectContext(IHostProject project, IPlatform platform, Boolean create)
en Microsoft.Expression.DesignSurface.Project.ProjectContextManager.GetSourceItemContext(IHostSourceItem sourceItem)
en Microsoft.Expression.DesignSurface.DesignerService.CreateDesigner(IHostSourceItem item, IHostTextEditor editor, CancellationToken cancelToken)
en Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteDesignerService.<>c__DisplayClass10.<>c__DisplayClass12.b__f(CancellationToken cancelToken)
en Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteDesignerService.CallWithCancellation[TResult](IRemoteCancellationToken remoteToken, Func`2 func)
en Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteDesignerService.<>c__DisplayClass10.b__e()
en Microsoft.Expression.DesignHost.Isolation.Remoting.ThreadMarshaler.<>c__DisplayClass16`1.b__15()
en Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.Call.InvokeWorker()

Hola, tengo problemas al abrir un nuevo proyecto de windonws phone
1.- abro el visual 2012
2.- Ctrl+Mayus+N (nuevo proyecto)
3.- Elijo plantillas - C# - Aplicacion de windonws phone
4.- framework 4.5 aparece por defecto
5.- luego, elijo windons phone OS 8.0 ó windons phone OS 7.1
6.- me sale el error que publique arriba, cuando carga el diseñador (MainPage.xaml)
* (el simulador solo funciona con O.S 7.1 funciona)

reinstala el sdk, tienes errores en las plantillas