Dear NB3004,
Thanks for including a screenshot of your problem, now it makes alot of sense.
What has happened is that FCP has imported in stereo, which it does, but you have one channel of sound and one channel of nothing.
I can see from your timeline that your sound is locked together. All you do is unlock the sound channels, delete the 'blank' one and then duplicator as previous discussed in this thread. Once you have the sound channels together, you can relock them, so if you need to move them about, life is a lot simpler.
To unlock sound channels:
1. Select the sound in the timeline. If you have not done so already, you need to unlink the video with the sound. To do this, simply press 'Cmd-L'.
2. Then go to "Modify > Stereo Pair" or press 'Option-L'. This will seperate the sound channels.
Simply as that. Please see screenshot for more help.
Hope this helps...