I'll try to be clearer about this bug. I hope it helps and someone confirms it.
It's been happening to me in all released versions since DViewcam version 3.0 (first one I tried). I have Windows 7 64bit, DCS-2121s and my Dviewcam is configured to play the audio from one of the channels.
I figured I had two different experiences:
1) Particuarly in my last install, when I start the machine, DViewcam starts minimized and the warning "primary disk for both the OS and Dviewcam storage (...)" comes up. Accepting this message stops the audio.
2) On previous installs, I had set up DViewcam storage on a secondary HDD so that message did not come up, instead, in order to stop the audio I had to open the main console and minimize it again.
It's like the audio plays while DViewcam is in the background since windows starts, whenever you focus on the Main Console and minimize it again to the tray then the audio stops as it should. I think the Main Console does not start in the background entirely correctly.