Code:
/www/virtual/skling/www.porndozo.nl/video/solointerviews-adrianna-2.wmv -o /www/virtual/skling/www.porndozo.nl/flvideo/1189297390881700463.flv -of lavf -oac mp3lame -lameopts abr:br=56 -ovc lavc -lavcopts vcodec=flv:vbitrate=500:mbd=2:mv0:trell:v4mv:cbp:last_pred=3 -srate 22050 -lavfopts i_certify_that_my_video_stream_does_not_use_b_frames

You missed path to mencoder.

What is the content of include/config.php (remove database password on posting).