I am using a query

SELECT qry.txtRootCause, Count(tbl.txtRootCause) AS CountOftxtRootCause
FROM tblA AS tbl, qryRootCause AS qry
WHERE (((tbl.txtRootCause)=[qry].[atnRootCauseID]) AND ((tbl.dateIdentified) Between [Forms]![frmStratificationOfRootCauses]![startDate] And [Forms]![frmStratificationOfRootCauses]![endDate]) AND ((tbl.txtDepartment)=[Forms]![frmStratificationOfRootCauses]![cboDepartment] Or [Forms]![frmStratificationOfRootCauses]![cboDepartment] Is Null))
GROUP BY qry.txtRootCause, tbl.txtRootCause
HAVING (((Count(tbl.txtRootCause)) Is Not Null) AND ((tbl.txtRootCause) Is Not Null))
ORDER BY Count(tbl.txtRootCause) DESC;

But the problem I am having is when i try making chart with this query on report. It works fine for the first time and then it doesn't work.