ffmpegx conversion produces empty files

[aherodias]

Converting MP4 file to MP3 audio, the resulting file is empty. (BTW, I have worked this successfully in the recent past, but I had to reinstall my OS X and thus my FFMPEGX)
Here is the log:

Encoding started on Sat Jun 25 18:02:37 MST 2011
FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
Mac OSX universal build for ffmpegX
libavutil version: 49.0.0
libavcodec version: 51.9.0
libavformat version: 50.4.0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Volumes/My Book/X-files/MUSIC FOLDER/Environmental songs/_Clear Blue Skies_ (Live 1985).mp4':
Duration: 00:04:13.2, start: 0.000000, bitrate: 234 kb/s
Stream #0.0(und): Audio: aac, 44100 Hz, stereo
Stream #0.1(und), 29.92 fps(r): Video: h264, yuv420p, 480x320
Codec type mismatch for mapping #0.1 -> #0.0

[Case]

Your source file has audio as stream #0.0, and video as stream #0.1. ffmpegX expects that reversed.
To encode the audio of this movie file to MP3, de-select the Invert mapping checkbox in the Audio tab.