formulas calculating incorrectly

Hello all.

This is my first time utilizing this forum. First and foremost, I appreciate your time and input.

Here's my issue: I'm using an excel spreadsheet/report generated from one of my colleagues in another department to pull out selective data. However, the formulas are calculating incorrectly. They don't seem to recognize the data from the report. For example, in one portion I'm trying to determine how many instances of a scenario occur within a certain date range. A simple array formula that has worked for me a thousand times before isn't in this spreadsheet (example below). I've made sure that the dates are formatted as such and other details I'm aware of that would affect these calculations.

Can you assist me in trouble-shooting?

Below is an example. Please keep in mind that when I open a new spreadsheet enter in dates and try these formulas out, they work fine. I'm perplexed.

=SUMPRODUCT(--(D10:D183>=DATE(2009,8,9)),--(D10:D183<=DATE(2009,8,15)))

My objective here is to count those dates that fall into the given date range. I'm then going to add another criteria, but this is a start.

Thanks again!