When I try to watch the McClanahan videos (the others that I’ve tested seem fine) on my Mac (running OS X 10.7.3) in either Safari (5.1.5) or Firefox (10.0.2), I see the video fine but there’s no audio. I downloaded the m4v files and tried to play them in iTunes, but again, no sound.
I “fixed” the problem by opening them in HandBrake, “adding” a second audio track, setting the second track to “Auto Passthru”, and re-encoding the file to a new one. When I add the new file to iTunes, it appears to play correctly.
Just thought I’d let everyone know in case others have the same problem.