perhaps this post will help:
Also see the last answer in http://www.apertureexpert.com/forum-user/post/1961311
Thanks but I dont have any presents. When the dialog box came up from Nik, I tried 3 times to enter me serial number and kept getting the errors.
I looked on my user preferences file and noticed the SilverEfexPro2.cfg did not have the key in it, which I did find in /System/Library/Preferences/Nik Software/SilverEfex Pro 2 - I copied this file into my user preferences file, but it did not help.
It does make me question why SilverEfex stores a serial number in a text file, but thats another fish to boil.
Thanks for the help. I am waiting to call Nik to authorize software I really do not need to be authorizing.
Making users do some manual mumbo fumbo to save their plugins is the reason I dont use Windows Apple, please do better.