I have had the same problem before. I would check out the FTC program training site:
http://www.education.rec.ri.cmu.edu/content/events/ftc/ There is a video under labview thats called using the FTC controller station.
You can go under the program that you chose to use and view their tutorial on how to connect via BT. From the top of my mind, I can think of two reasons, one is that somehow you've got your NXT's name wrong, and two, you are trying to connect a NXT-G controller station to the Labview's firmware.
Anyway, I hope the video helps
