Designer error vs2012

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WPF

hi
I using vs 2012 and i have problem with all wpf application .Designer not working
and show this error:

Error pic : http://file123.persiangig.com/Error.PNG[^]

Details:
System.Runtime.Remoting.RemotingException
[] Designer process terminated unexpectedly!
at Microsoft.Expression.DesignHost.Isolation.Primitives.ProcessDomainFactory.ProcessIsolationDomain.Microsoft.Expression.DesignHost.Isolation.IIsolationDomain.CreateInstance(String assemblyName, String assemblyCodeBase, String typeName)
at Microsoft.Expression.DesignHost.Isolation.Primitives.IsolationBoundary.Initialize()
at Microsoft.Expression.DesignHost.Isolation.Primitives.IsolationBoundary.CreateInstance[T](Type type)
at Microsoft.Expression.DesignHost.Isolation.IsolatedExportProvider.Initialize()
at Microsoft.VisualStudio.ExpressionHost.Services.VSIsolationService.CreateExportProvider(IIsolationTarget isolationTarget, ICatalogFactory catalogFactory, IExportFilter filter)
at Microsoft.Expression.DesignHost.Isolation.IsolationService.CreateLease(IIsolationTarget isolationTarget)
at Microsoft.Expression.DesignHost.IsolatedDesignerService.CreateLease(IIsolationTarget isolationTarget, CancellationToken cancelToken, DesignerServiceEntry& entry)
at Microsoft.Expression.DesignHost.IsolatedDesignerService.IsolatedDesignerView.CreateDesignerViewInfo(CancellationToken cancelToken)
at Microsoft.Expression.DesignHost.Isolation.IsolatedTaskScheduler.InvokeWithCulture[T](CultureInfo culture, Func`2 func, CancellationToken cancelToken)
at Microsoft.Expression.DesignHost.Isolation.IsolatedTaskScheduler.<>c__DisplayClassa`1.<starttask>b__6()
at System.Threading.Tasks.Task`1.InnerInvoke()
at System.Threading.Tasks.Task.Execute()




already Desginer working well and not problem , but now occur this exception.
Do you have a good idea of how to solve problem?

this is test project with out custom layout or codebehind.

<Window
	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
	x:Class="WpfApplication2.MainWindow"
	x:Name="Window"
	Title="MainWindow"
	Width="640" Height="480">

	<Grid x:Name="LayoutRoot"/>
</Window>