Jeff has linked to a thread that should solve the issue. Now, did you ever Copy/Paste the Audio? That could well be the cause. In my experiences, the Copy/Paste can have a delayed reaction - things go well for long enough to give one a false sense of security. Then, maybe it's a Render (after dozens of others), or the phases of the Moon, but suddenly, things go flatline. Going back to the old forum, I had a very long, and interesting thread on this in PrPro 2.0. Lot of great conversation, but the final solution is as Jeff suggest - Match Frame, and all should be well. Follow the instructions to both Select the Clip and also position the CTI over it. The exact keystroke will differ by version #, but I think that thread covers all bases, due to my early mistake.
Thankyou so much Bill & Jeff!
I've only just been able to get back to the project - and the Match Frame
function worked exactly as you said (keystroke 'm' in CS3).
The problem probably was the result of copying and pasting (a common habit
of mine), as you suggest.
Thanks again - very much appreciated!
Great news, and glad that it worked for you. Most of us use Copy/Paste often. In my observations, often things work fine. Other times, the Audio gets lost immediately, and in my case, only after multiple Renders. Things worked fine all day, and then on say the 30th Render - Boom, flatline Audio for all Clips that were Pasted.