I think a couple of people have mentioned that music or voiceover audio was not present in their published videos. I may have experienced the same symptom.
Today when I imported my voiceover, it was immediately set to zero volume. Once I noticed, I changed the volume to 100% and continued working on my project. The audio then worked normally for a while while I edited and previewed the project. About halfway through my editing, although I did not access the audio properties menu, The audio went silent again. When I opened the audio properties, I saw that the volume slider had returned to the zero position. I again returned it to 100%. It remained there until I rendered the video, at which time it returned to zero volume and the video file was silent. I reset the volume to 100% again and the video rendered correctly.
I'll post more information if any new details reveal themselves.
Hey Mike, that's not one I have seen before. I'll turn this into a ticket and if you can confirm the version you are using and send us a copy of the project we'll do some testing around that and see what we can uncover.