I just posted a note of the identical problem, then found this message chain.
I tried Chienworks' idea, but didn't come up with the choose channel option. In fooling around earlier, I thought I came accross something of that nature, but I can't find it now. Any other suggestions?

I had a similar problem but it was the left channel that had the audio. Here is what I did (please keep in mind that I am not at my home computer, so things may not be exact):

1) Downloaded a copy of Audacity (freeware program).
2) Configured Movie Studio so that Audacity would be my audio editor.
3) Right clicked on the audio track in MS, then selected 'Open copy in audio editor'.
4) Once in Audacity, Split the single stereo track into two single tracks.
5) Select All on the blank or empty audio track and delete the wave form (right track in my case).
6) Select All on the audio track that has the sound on it (left track in my case).
7) Copy and paste the audio track with sound on it to the empty track (copy left track to right track in my case).
8) Join the two separate audio tracks back into one single audio track.
9) Export the track out as a .wav file and give it a new name (I was just adding an 'a', 'b', etc. suffix to the file name).
10) Go back to Movie Studio and delete the audio track.
11) Import the new audio track into the media pool.
12) Add the new audio track to the timeline.

This may seem like a lot of steps, but it does work and once you do a few of these, you will get a lot faster at it.

If there is an easier way (and I am sure there is), please let us know.

Thanks...
Al