I uninstalled/reinstalled Wavepad, upgrading to the latest version (v 5.96). Didn't help.
I installed Switch. Same problem.
I tried another program (AOA audio extractor, free version), it extracted the audio just fine.
I guess there's not much else I can do to extract it with the NCH programs.
I then proceeded to edit the extracted audio file in Wavepad. Works just fine. (Wavepad is a great program, by the way. It's just very nice and easy to use. Thank you!)
I'm running Windows7, 32 bit OS.