On Fri, 4 Jun 2010 10:03:09 -0700, RAK
wrote:

ISNUMBER shows true that it is a number - it is generated by a formula

Please post the formula.

Also, if it is truly a number, then your problem is that your value in
the SUMIFS criteria, and the value in the SUMIFS criteria range, are
not exactly the same. There may be extra spaces, or nbsp's or other
contents difficult to see.