what's layer 20? Those sort of errors shouldn't matter. What does the ERC say? I'd also get the DRC file from Lain, it will go beyond the stock DRC.
Also: put your meter between +5 and GND, +12 and ground, -12 and ground an make sure you dont have continuity. I dont know the details of what the short circuit protection there is on the DAC but if there isnt any, a short on either of the 12V rails would cause that failure so poke around those traces