Brian,
I agree with Kanturina. Renaming a .VOB (video object) file to an .m2v is the simplest method of operation here, and works well most of the time.
Another possibility would be to use Adobe Audition (if you have that as well). You can capture audio from video directly using that program. Go to the FILE->OPEN AUDIO FROM VIDEO. If it is a very long program, it can take a while to capture into Audition.
Finally, if you have a PC available to you for this task, you could use an excellent program called Total Recorder. Anything you can hear on your computer’s speakers, it can capture.
Rather than being an analog means of capturing, it actually taps into your soundcard’s digital output and diverts (splits) the audio there to Total Recorder. So the sound is pristine and undistorted, with no additional D/A or A/D conversion necessary. Very, very cool program, and it has saved my rear on numerous occasions.
FYI, Total Recorder runs with very little resources (as compared to Camtasia Studio, which is a huge memory hog!). You also still hear the audio coming from your speakers normally, so it changes nothing during playback and capture. Best of all, it supports a wide range of audio file formats.
Scot