silverlight-4.0 - Silverlight 4 在打开项目时出错

Question

我在 VS 2010 中安装了 Silverlight4，它运行得很好，但是现在当我打开它时，我得到了这个错误：

System.NullReferenceException
Object reference not set to an instance of an object.
   at Microsoft.Windows.Design.Platform.SilverlightMetadataContext.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(PrefixScope parentScope, IParseContext context)
   at MS.Internal.Design.Markup.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.FullParse(Boolean convertToXamlWithErrors)
   at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.get_RootItem()
   at Microsoft.Windows.Design.DocumentModel.Trees.ModifiableDocumentTree.get_ModifiableRootItem()
   at Microsoft.Windows.Design.DocumentModel.MarkupDocumentManagerBase.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.VSIsolatedView.Load()
   at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedDesignerFactory.Load(IsolatedView view)
   at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)
   at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(IsolatedDesignerFactory factory, IsolatedView view)
   at MS.Internal.Host.Isolation.IsolatedDesigner.Load()
   at MS.Internal.Designer.DesignerPane.LoadDesignerView()

我有运行时版本。有什么建议么？:-)