No audio after 2nd-pass

[dchui]

I am using FlaskMPEG 0.594 with Divx Pro 5.05 and Radium mp3 codec. My first attemp of converting a dvd movie into avi (using one pass only) was completed with no problem except the video quality is not so good. So I decided to try to convert it again using multi-pass this time but only converting the last vob file (instead of converting the entire movie which takes about 10 hr on my computer). The final result after the 2nd pass gives me excellent quality of video but no audio. Does anyone know why ?