As nobody has offered you assistance in your time of need, I suggest you go to www.askthebuilder.com, click on flooring and then scroll down to an article called "Wood floors that bounce and creak".
The article says that with hardwood the issue could be simply loose nails which squeek when you walk on the boards which flex. I would suggest finding the offending nails (if possible) and replace with similar ones with barbs so they won't pull out. You didn't say the flooring was bouncy, which is a more serious problem according to the article.