No, it didn't work on my Mac either
Having to slum it now, and use the other half's Windows 8 machine instead
I know the feeling!! Uni computers are windows. horrible machines

I got it to work this afternoon though, You need to get the unarchiver from the app store, download the file from the nav website as usual and then when you open it, it automatically decrypts it into the same format as the ones on the SD card, i made a copy just incase but just replace the old files with the news ones and it worked for me