There may be a way to stop your Mac always asking for administration rights to authorise change but it would surely entail some really serious under-the-bonnet tinkering on your Mac using Terminal code, but again I don't have direct expertise on this issue so I'd only be googling & if I struck it lucky, passing the method to you to follow at your own risk.
I have been doing extensive googling on this issue with not much luck really but the following might offer a solution with the emphasis on
'might'.
Some have found changing from the BigPond Connection Manager software/drivers to the Netgear AirCard/drivers have helped but usually for connection issues not specifically your issue.
AirCard 320U (BigPond)
You can only give it a whirl but I am using Mac OS X 10.7.5 & cannot replicate your issue.
If you google aircard 320U usb modem & click on the images tab you will see that your USB device is shown amongst the results so don't be confused by this …
All I can suggest is that you either give the AirCard software a go over the BigPond Connection Mgr software
OR
you can
book an Telstra Tech Bar appointment & make sure you can take both your Mac & the device in to Telstra so they can see exactly what you're seeing …. well that's my 2¢'s worth hope it helps