possibly:
i = DCount("SendingDept", "maintable", "SendingDept='AACP' _
and RDateMPU>=#" & Format(Combo1, "mm/dd/yyyy") & "# _
and RDateMPU<=#" & Format(Combo3, "mm/dd/yyyy") & "# _
and reason like 'No Frontsheet Attached*' ")
it sounds like one of the parameters entered is the wrong...