в файле в котором ошибка заменить
select a.Sub_Class_ID,a.Sub_Class_Name,b.Class_Name,a.Priority,a.Checked,a.Class_ID,a.EnglishName,d.Domain,c.Hidden_URL from Sub_Class AS a,Class AS b LEFT JOIN Subdivision AS c ON a.Subdivision_ID=c.Subdivision_ID LEFT JOIN Catalogue AS d ON c.Catalogue_ID=d.Catalogue_ID WHERE a.Subdivision_ID=".$loc->SubdivisionID." and a.Catalogue_ID=".$loc->CatalogueID." and a.Class_ID=b.Class_ID
на
select a.Sub_Class_ID,a.Sub_Class_Name,b.Class_Name,a.Priority,a.Checked,a.Class_ID,a.EnglishName,d.Domain,c.Hidden_URL from ( Sub_Class AS a,Class AS b ) LEFT JOIN Subdivision AS c ON a.Subdivision_ID=c.Subdivision_ID LEFT JOIN Catalogue AS d ON c.Catalogue_ID=d.Catalogue_ID WHERE a.Subdivision_ID=".$loc->SubdivisionID." and a.Catalogue_ID=".$loc->CatalogueID." and a.Class_ID=b.Class_ID