Try this sql statement instead of yours to output the sql and check if the values added into maybe contain incompatible content like comma for example:
Debug.Print "Insert INTO tbl_InvoiceItems" & _
"(InvID,ItmID,ItmSID,ItmSaleBalance,InvItmQty,InvItmPrice) VALUES " & _
"(" & me.Parent!InvID &...