RD, thanks anyway. Yeah, I do select the Denon directly and not the system default device.
In thinking about this some more, I'm beginning to think that the problem is with MC running when the machine wakes up if the set device isn't available, it has to select something else. However, the next time the system wakes up, MC is still running pointing at whatever device it thought it could find, which of course is still there, and there's nothing causing it to go search for the Denon again. So it just sits there pointing at the headphone device. Unless there were some code causing it to detect the system waking up and forcing it to search for the Denon, nothing will happen.
This is just speculation on my part, but would appreciate someone from JR commenting on it.
Thanks again