I did as suggested, and here's what happened:
After renaming the .conf file, the Audio Master Out worked just fine.
On loading my project, and taking care to remove previously connected busses, things went sour, just as before.
I really don't know if there's any sort of corruption in the file...
Maybe, just maybe, I might just redo everything, or even start a new project from scratch, and see what transpires.
Thanks a whole lot for bearing with me.