Problem with audio/midi control

Hello, I am new to this forum, and new to organs in general.
I had installed GrandOrgue on my MacPro (2009, 12 cores, 24G RAM) and it was running fine. However, I could only get the audio to come out the headphone jack, not out USB and into my external DAC. The DAC works fine for other applications. I tried to add an output device in "Audio Output". Still no output to the DAC. So I deleted the default, original device. The application froze up, and I had to force quit.
After restarting the computer, reinstalling GrandOrgue, cleaning all caches (using Onyx) I cannot launch the Audio/Midi Settings pane without the program freezing.
Any help would be GREATLY APPRECIATED since I am dead in the water right now......

Thank you Martin! It works again, but still can't get it to output via the DAC. At least the headphone out works now.
Another newbie question: I have never played an actual pipe organ, so I don't know, but it seems like the delay between pressing a key and pipe sounding is excessive, even in high notes. Is this normal or is there some setting I'm missing?
Thanks a million
Dave