Reply to Traktor - headphone cue on master, no idea how to fix

So my new Mixtrack Pro 2 arrived today and I thought I'd play with the integrated soundcard. It worked fine for a few hours and then Traktor started playing whatever I was doing on the headphones to the master output. I have no idea what happened. The headphones play only the cue signal, while my speakers play both the monitor and the master output. I tried unplugging everything, restarting traktor and my computer, re-doing the settings from scratch to no avail.

I'd appreciate any help. Has anyone ever had this problem?