problem with SUMPRODUCT looking to match a date range

Hi can someone help me with this formula I am having a few problems with:

=IF(ISNUMBER(G12),SUMPRODUCT((RE_Names=INDIRECT("'Holidays'!C"&COLUMNS($A:I)))*(RE_Dates>=Holidays!$D$3)*(RE_Dates<=Holidays!$E$3)*(RE_Shifts="HOLS")),"") is returning a 0 when it should be returning a number.

The problem is with Holidays!$D$3 and Holidays!$E$3. They are set to ="01/07/"&YEAR('Extract'!O4) and ="30/06/"&YEAR('Extract'!O4+200) which display 01/07/2013 and 30/06/2014 respectivly. The cells they are in are formatted as a date but the formula doesn't work. It will only work if i type the dates manually.

Has anyone got any ideas?

John

="01/07/"&YEAR('Extract'!O4)+0 worked.

Thanks Pepe