I had the same problem so I downloaded this version of the adb.This crazy I finally get everything working on the NC but now I need to install Market and google services. I finally am able to get the NC to be recognized by my win7 x64 as "Android Composite ADBInterface" and when I goto execute cmd line the device is offline. what gives. Any help would be welcome.
[DRIVER PACK] Easy USB ADB Installer for Windows (32/64 bit) - xda-developers
And then my computer recognized my NC.