NetworkManger has two parts one is run on the system level to 
manager connections and gather information. The other is an applet
the user can interact with. Since NetworkManager is not part of
main yet, you have to add nm-applet to your session once.

(instructions for gnome only)
First add yourself to the plugdev group
Go to System -> Preferences -> Sessions
In the Startup Programs tab, click Add
type "nm-applet", click OK.
log out of your gnome session, and log back in again.