Sony Vegas 6.0 .MP4 Audio Not Working

Help! I am currently using the 6.0 version of Sony Vegas. My Olympus Sp-800uz records videos to a .MP4 file, and 6.0 has been able to recognize it just fine up until today. For some reason, it is saying that there are no sound waves. I opened up the file in QuickTime, and realized that the video had no sound! However, I did download VLC media player, and it had perfect audio. I also download a trial of Sony Vegas 11.0 and it worked fine.

Vegas 6.0 Baby