Update 3.16
Posted by: Stephen Pritchard on 15 September 2012
Do you have windows running in your iMac. The instructions say:
A PC running Microsoft Windows XP, Windows Vista or Windows 7, and incorporating an RS232 port (or USB port - see bottom of page) is required to undertake the update. The NaimUniti to be updated must be switched on, working correctly and connected to the Internet and an RS232 (or USB port) port while the update procedure takes place.
NaimUniti, UnitiQute, NDX
Requires 9 pin to 9 pin RS232 serial cable (or USB to Serial converter - ones with FTDI or Prolific drivers are suggested.
I am pretty sure it is PC only at the moment with Mac support to come. Are you a Bootcamp or Parallels user? Having said that I could not update my NDX to 3.16 with my Macbook Pro retina as it said it needed USB drivers then the drivers did install successfully.
The instructions are pretty clear, with a link to the required cable.