Partial Sound not Working

[Mich85]

I'm VERY new to videopad and am just trying to get home videos onto my computer so I can share them. It was going well but now is starting to have trouble. I have one video that plays just fine with all of the sound outside of videopad but whenever I bring it in to clip it, there is one portion of the video that has no sound at all. I've tried clearing the cache and I've tried taking it out and putting it back in and it's the same place every time, NO SOUND. Any suggestions on what to do. When just playing in the video player on  my computer it works just fine, plenty of clear sound but just about 20 minutes of my 60 minute video (in the middle) No sound. Help me please. It's an important clip that I need to transfer.