Is NETWORKDAYS giving you the wrong results? It seemed that it was for me. I had ten holidays listed, but it was only subtracting eight! Well, I spent about ten minutes trying to figure it out, then I gave up and googled it. Norman Harker provides the (obvious) answer here:
The problem was that some of the holidays land on Saturday or Sunday. Dang, there’s some brain cycles I can never get back. Thanks to the anonymous person who presented this problem.