Welcome to the forum.
First, more information would be useful. See this FAQ Entry for what info will help: http://forums.adobe.com/thread/961741?tstart=0
Also, when you Import your AV file, do you allow PrPro time to Conform the Audio portion? For more info on Conforming, Indexing and PEK file creation, see this article: http://forums.adobe.com/message/3892177#3892177