Knowledge Articles Quick Find error

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=9.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: System.Xml.XmlException: Microsoft.Crm.CrmException: An unexpected error occurred.
   at Microsoft.Crm.Application.Platform.ServiceCommands.PlatformCommand.XrmExecuteInternal()
   at Microsoft.Crm.Service.Application.Platform.ServiceCommands.FullTextSearchKnowledgeArticleCommand.Execute()
   at Microsoft.Crm.ApplicationQuery.FullTextSearchKnowledgeArticleAnswersByBodyApiCommand.RetrieveData(String searchText, Guid searchSubjectId)
   at Microsoft.Crm.ApplicationQuery.SearchAnswersApiCommand.RetrieveData()
   at Microsoft.Crm.ApplicationQuery.ExecuteQuery()

t System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously): Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #FFADE7ADDetail: 
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
  <ActivityId>02be01e9-9e94-457f-a98b-87c5ad4034e6</ActivityId>
  <ErrorCode>-2147220970</ErrorCode>