I think I have figured out what's happening in that library. As I mentioned, the sampling loop just goes as fast as possible. Your code sets the sampling rate to 9000Hz but I've measured that loop on my Duemilanove with a frequency counter and the loop is more like 8300Hz.
Change your sampling frequency to 8300 and give it a try. On my Arduino it shows a definite peak at 440Hz now.
Pete