Ok, I think I have figured this out. When the script convers a video, it executes the following command.

/usr/bin/mencoder /home/userdir/public_html/video/dream_kelly_on_bed.wmv -o /home/bolek/public_html/video/1.flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=500:mbd=2:mv0:trell:v4mv:cbp:l ast_pred=3 -srate 22050 -lavfopts i_certify_that_my_video_stream_does_not_use_b_fram es

and when I type which ffmpeg I get the following out put.

[root@server ~]# which ffmpeg
/usr/local/bin/ffmpeg

It appears this is installed in a directory not compatible with the script. If I run the ollowing I actually get a reply.

/usr/local/bin/mencoder /home/userdir/public_html/video/dream_kelly_on_bed.wmv -o /home/bolek/public_html/video/1.flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=500:mbd=2:mv0:trell:v4mv:cbp:l ast_pred=3 -srate 22050 -lavfopts i_certify_that_my_video_stream_does_not_use_b_fram es

It appears this needs to be installed in the /usr/bin/ directory. Is this correct?