problem when mappping mainReport and subReport using date fields

[Jury Buono, Computer Time & Geco Informatica]

Hi, hi have make a 

mainReport from query like this :   select numInvoice, dateInvoice, CodArt, Color, Qty from artInvoice

subReport form query like this   : select name,numInv, dateInv from invoice 

then i link maniReport and subReport with function “Field Map”
and i have associate 

mainReport Field		SubReport field

numInvoice			numInv				this fields ares numeric data type
dateInvoce			dateInv				this fields ares date data type

if i made this links the report show only main report and not sub report 
if i made this links without dates all work fine
i check if dates in main query and sub query are equal and the result is yes 
can anyone help me please  ??
sorry for my bad english, J.B.