It can return FALSE because of the end of the formula:
Change AVERAGE($J$2:$J$3536,"")) to AVERAGE($J$2:$J$3536),"")

"PAL" wrote in message
...
This formula returns a "false" but should return a number: As an
array.....

=IF(AND($I$2:$I$3536"",$H$2:$H$3536"",$H$2:$H$35 36=10/1/2008,$H$2:$H$353611/1/2008),AVERAGE($J$2:$J$3536,""))

Columns I and H are dates.

Thanks.