An error occured while attaching module (Dynamicweb.Frontend.Content)

System.Data.SqlClient.SqlException: The ntext data type cannot be selected as DISTINCT because it is not comparable.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()
   at System.Data.SqlClient.SqlDataReader.get_MetaData()
   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
   at Dynamicweb.Database.getDataReader(String SQL, String Database, Int32 timeout)
   at Dynamicweb.eCommerce.Products.Group.get_CachedGroups()
   at Dynamicweb.eCommerce.Products.Group.get_AllGroupsByLanguageID(String languageID)
   at Dynamicweb.eCommerce.Products.Group.get_GroupByID(String groupID)
   at Dynamicweb.eCommerce.Products.Group.GetGroupsByIDs(IEnumerable`1 groupIDs, Boolean applyFiltering)
   at Dynamicweb.eCommerce.Products.ProductGroupRelationCollection.get_GroupCollection()
   at Dynamicweb.eCommerce.Products.Product.get_Groups()
   at Dynamicweb.eCommerce.Products.Product.GetCategories()
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProductCategories(Product product, Template template, String loopName)
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProduct(Product Product, Boolean ExtendedProperties, Template Template, Int32 loopCounter, Boolean renderRelated, String productURL)
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProduct(Product Product, Boolean ExtendedProperties)
   at Dynamicweb.eCommerce.Frontend.Frontend.RenderProduct(Product prod)
   at Dynamicweb.eCommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.eCommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.getModule(DataRow& ParagraphRow)