When I want to use an updated audio file that I have saved under the same file name as previously used audio file, Captivate doesn't replace the old one (at least not in the timeline). I have to save the updated audio file under a different file name. Small detail, but in other Adobe products (e.g., Premiere Pro), I replace the old file with the new one (same name) in the source folder and voila - replaced in my timeline...