SUMPRODUCT errors dealing with dates

[BeeFreedman]

I have a column of dates in K6:K46 that are in 2005 and 2006.

I want to count the dates that fall between lower and upper limits I specify (as variables). The lower limit dates are in column A and the upper limit dates are in column D.

I am using this formula:
=SUMPRODUCT(($K$6:$K$46 > $A7)*($K$6:$K$46 <=$D7))

The formula works when A and D are both in the same year. But when A is in 2005 and D is in 2006, it counts either ONE too many or TWO too many (I cannot see any pattern to this error).

I cannot debug this and will appreciate any help you can give. Thanks.

[richardreye]

That's strange because it works fine on my computer using Excel 2003.

[BeeFreedman]

I am using Excel 2000. I am going to go hassle my IT department for Excel 2003 and see what happens. Thanks!