What would make this not work:

=SUM((Time1!$L$2:$L$529=$A77)*(Time1!$H$2:$H$529=D$1)*Time1!$J$2:$J$529)

When this does:

=SUM((Time1!$L$2:$L$524=$A77)*(Time1!$H$2:$H$524=D$1)*Time1!$J$2:$J$524)

All I've done was extend the number of rows being checked for SUM (from 524 to 529), but somehow it returns 0 where the original returns the expected sum. Those rows after 524 aren't any different than those before.

I'm baffled. Any help would be great.

Thanks!