عدم لود صفحه دیزاین

[barbodsoft.com]

سلام
من مدتی می خوام با سیلور لایت کار کنم ولی صفحه دیزاین اون لود نمی شه و بجای آن پیغام زیر نوشته. پروژه رو مجدد بیلد می کنم ولی فایده ای ندارد.


System.NullReferenceException
Object reference not set to an instance of an object.
at Microsoft.Windows.Design.Platform.SilverlightMetad ataContext.SilverlightXamlExtensionImplementations .<GetXmlNamespaceCompatibilityMappings>d__8.MoveNext()
at MS.Internal.Design.Metadata.ReflectionProjectNode. BuildSubsumption()
at MS.Internal.Design.Metadata.ReflectionProjectNode. SubsumingNamespace(Identifier identifier)
at MS.Internal.Design.Markup.XmlElement.BuildScope(Pr efixScope parentScope, IParseContext context)
at MS.Internal.Design.Markup.XmlElement.ConvertToXaml (XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
at MS.Internal.Design.DocumentModel.DocumentTrees.Mar kup.XamlSourceDocument.FullParse(Boolean convertToXamlWithErrors)
at MS.Internal.Design.DocumentModel.DocumentTrees.Mar kup.XamlSourceDocument.get_RootItem()
at Microsoft.Windows.Design.DocumentModel.Trees.Modif iableDocumentTree.get_ModifiableRootItem()
at Microsoft.Windows.Design.DocumentModel.MarkupDocum entManagerBase.get_LoadState()
at MS.Internal.Host.PersistenceSubsystem.Load()
at MS.Internal.Host.Designer.Load()
at MS.Internal.Designer.VSDesigner.Load()
at MS.Internal.Designer.VSIsolatedDesigner.VSIsolated View.Load()
at MS.Internal.Designer.VSIsolatedDesigner.VSIsolated DesignerFactory.Load(IsolatedView view)
at MS.Internal.Host.Isolation.IsolatedDesigner.Bootst rapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)
at MS.Internal.Host.Isolation.IsolatedDesigner.Bootst rapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)
at MS.Internal.Host.Isolation.IsolatedDesigner.Load()
at MS.Internal.Designer.DesignerPane.LoadDesignerView ()