Further to Wrzwaldo's post.. Have you read the Readme that was included with the Netstumbler software ?
If you only see your own AP and you know for a fact there are other AP's in the vincinity that you should be able to see, my guess is you haven't read the part of the Readme file, that explains how Netstumbler should be used..
Hint (festive season mode still in effect, you lucky bastard
) : Do NOT use Netstumbler while associated to an AP.
Dutch