Reply to Denon DNX 1600 and Mac 10.8.4 audio issues

Hi guys I have not used my mixer for a while utilising the internal sound card with Ableton and my Mac running 10.8.4, to be honest I can't remember if I'v used my new Mac (Late 2012 I7 8gb) with it, my old mac however (Later 2008 C2D 2gb running 10.6.8) ran flawlessly with it.

Anyway, when trying to playback audio through Ableton to my mixer it is really choppy and gets distorted every few seconds, i'v checked the sample rates match and tried raising my latency etc but still the problem continues. I tried running another program aswell and encountered a very similar but not the same audio problem.

Any ideas?