Can u post your code if possible..?
Since I see a bit of interest in this, here is a cheap-n-dirty version of my guitar tuner. It was written to work with frequencies as low as A0 (27.5Hz) and as high as G6# (1661.218Hz). Please feel free to critique and/or comment on it. I added the ability for the user to change the "tolerance" for a note to be consider "just right" (tuned properly). By default, it is +/- 0.2% of the note's ideal frequency. I also added the ability for the user to adjust the amplitude threshold for the mic input. It was based off of the "continuous sound input" example VI.
One thing I plan on doing is adding an actual list of available sound input devices instead of a [seemingly] arbitrary 0, 1, 2... numeric control for the input device.