Same problem… It was working fine until a few days ago. It happened when I unplugged the headphones from the macbook pro to connect an AUX 1/8" cable (so that I can play the mix through my home stereo system) and the sound started to come out of the macbook speakers only. So I plugged the headphones back thinking the AUX cable was the problem but nope… I was never able to make it work again afterwards. The headphone will only work when I hook up the laptop back to my 18i20 card, which is extremely inconvenient because I’m at a stage where I’d like to validate (and do minor tweaks on the fly) my near-final mixes using other references (like my home system and car) than my studio monitors.
Steinberg, what’s the word on this issue?