You are not going to like this but, I had the same situation about 2 months ago. I did advise the forum here and got alot of great ideas and feed back. Nothing worked.
I had alot of footage shot from a few different people and one interview had the same audio problems that you discribe. Listening to it is PPro was fine but output to dvd had issues everytime. I tried reformating the track, outputs of every kind.
Here is what I did. I could hear everythig just great through PPro so I set up my camera with a Lav mic in a perfectly quite room and played the video back on the computer were i could hear everything and re-recorded it into the camera & re-digitized it into the computer. It was clean and it was the best “work around” that i could come up with. The client kicking down the door was happy and so was i.
Media Meathead
Chris