[Max Davis]

I had the same problem also… pretty annoying!!!!

The problem was in my music files. I noticed that somehow when I converted my music in itunes as an aiff that it was 44k with 8 bit audio. This did not match my raw video’s audio which was 48k with 32bit audio.

During rendering these two different audio files didn’t like each other and caused some very undesirable problems on the final exported file.

So the solution was to go back to itunes and change my import setting to 48K 32 bit aiff audio. Then select the music file, create a new aiff and then reconnect the files in FCP.

When reconnecting in FCP it did warn me that some attributes were not the same, but hit continue anyways. This should force it to forget the old render files and re-render it with two files that actually like each other with the same bit rate.