Well, this is very late but I was hitting the same problem and finally found the solution in 10.6.
The problem resides in the file
If you open it and search deep inside, you will find a set of keys that say:
This is the translation of the network preferences pane in XML. In the System Preferences, I explicitly said I did not want to be prompted for a password when changing Airport status (on/off) or switching networks (SSID's). All these options are translated into "false" in this file.
There is however ONE key that I could not find reflected in the System Preferences Network pane... the simple short "RequireAdmin". This one here is set to "true" and there is no graphical element in the System Prefs to change it (not that I found at least). When that value is set to true (which is the case), SystemUIPreferences will prompt you for a password each time you do just anything to Airport via the system status bar.
We can fix that. The trick is to modify that value and then restart the SystemUIServer.
Operation 1: modify the preference file
open a terminal and edit the file with
yourname-mac:~ yourname$ sudo vi
Then search for RequireAdmin. Change the value of that key from "true" to "false". The file will now contain
Save the file and exit the editor.
Operation 2: restart SystemUIServer
From the terminal, search for the process SystemUIServer:
yourname-mac:~ yourname$ ps ax | grep SystemUIServer
387 ?? S 0:02.66 /System/Library/CoreServices/SystemUIServer.app/Contents/MacOS/SystemUIServer
96101 s000 R+ 0:00.00 grep SystemUIServer
The first entry is the right one -- the process SystemUIServer is started early on an will usually have a small process ID (PID). Here it is 387 but the numnber will likely be different on your system.
It is now time to kill the process -- MacOS will restart it for you and the new process will take your changes into account. Let's kill it now:
yourname-mac:~ yourname$ kill -9 387
The system menu applications flicker then re-appear. Try changing the Aiport status or switching network now... no password!