サイトをテンプレートとして保存しようとしていますが（そこから新しいサイトコレクションを作成するため）、[保存]を押すと次のエラーが発生します。また、サーバーを再起動して、SharePointを再インストールしてみました（無駄に）。何か案は？
Microsoft.SharePoint.SPException: Feature definition with Id b8455e32-8a67-4c15-9387-b3dd7e01cb4c failed validation, file 'T135PropertyBags\Elements.xml', line 2, character 62: The 'AlwaysCreateFolder' attribute is not declared.
at Microsoft.SharePoint.Administration.SPSolutionPackage.FeatureXmlValidationCallback.XmlValidationCallBack(Object sender, ValidationEventArgs evtargs)
at System.Xml.Schema.XmlSchemaValidator.SendValidationEvent(String code, String arg)
at System.Xml.Schema.XmlSchemaValidator.ValidateAttribute(String lName, String ns, XmlValueGetter attributeValueGetter, String attributeStringValue, XmlSchemaInfo schemaInfo)
at System.Xml.XsdValidatingReader.ValidateAttributes()
at System.Xml.XsdValidatingReader.ProcessElementEvent()
at System.Xml.XsdValidatingReader.Read()
at System.Xml.XmlReader.MoveToContent()
at System.Xml.XmlReader.IsStartElement()
at Microsoft.SharePoint.Utilities.SPUtility.XsdValidateXml(XmlTextReader xmlStreamReader, String friendlyName, String pathXsdFile, String tagExpectedRootNode, Int32 desiredPathVersion, ValidationEventHandler xsdValEventHandler)
at Microsoft.SharePoint.Utilities.SPUtility.XsdValidateXml(XmlTextReader xmlStreamReader, String friendlyName, String pathXsdFile, String tagExpectedRootNode, ValidationEventHandler xsdValEventHandler)
at Microsoft.SharePoint.Administration.SPSolutionPackage.SolutionFile.ValidateFeatureXmlFile(String rootTagElement)
at Microsoft.SharePoint.Administration.SPSolutionPackage.AddFeatureElementsCore(XmlNodeList nodeList, String strFeatureDirRelativeToCabFile, Guid featureId, Dictionary`2 filesAdded)
at Microsoft.SharePoint.Administration.SPSolutionPackage.AddFeatureElements(XmlNode root, String strFeatureDirRelativeToCabFile, String strFeatureXmlFilename, Guid featureId)
at Microsoft.SharePoint.Administration.SPSolutionPackage.WspSolutionFeature.ProcessFeatureXml()
at Microsoft.SharePoint.Administration.SPSolutionPackage.InitSolutionFeatures(XmlNode root)
at Microsoft.SharePoint.Administration.SPSolutionPackage.ProcessSolutionManifest()
at Microsoft.SharePoint.Administration.SPSolutionLanguagePack.CreateSolutionPackage(SPRequest request, String name, String signature, Byte[] fileBytes)
at Microsoft.SharePoint.SPUserSolutionCollection.<>c__DisplayClass4.<AddOrUpgrade>b__0()
at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode)
at Microsoft.SharePoint.SPUserSolutionCollection.AddOrUpgrade(SPListItem item, SPUserSolution existingSolution)
at Microsoft.SharePoint.SPUserSolutionCollection.Add(Int32 solutionGalleryItemId)
at Microsoft.SharePoint.SPSolutionExporter.ExportWebToGallery(SPWeb web, String solutionFileName, String title, String description, ExportMode exportMode, Boolean includeContent, String workflowTemplateName, String destinationListUrl, Action`1 solutionPostProcessor, Boolean activateSolution)