Does the computer recognize the the device? According to the Quick Start Guide, no USB drivers are necessary and it should be plug-and-play.
Are both RCA outputs, normal and pre, not working? Are you using only headphones?
It's brand new, I just got it today. I haven't tried either RCA, nor will I ever use them. I am only using headphones. I'm more concerned with the fact that Coaxial won't work, as there is not much that can go wrong other than something physical in the unit itself. It's more of a minor inconvenience as using the Line-in input is still outputting the best sound I've ever heard.
It is great that you got it working but since this is a new product under warranty you should contact them and get a replacement. All the inputs should be working. Also optical is usually limited to 24 bit 96khz and the DAC is capable of 24 bit 192khz through the other inputs. You can download free high resolution audio files with links from this site: