Audio Video Sync Problem

HI guys!

I use Auto Gordian Knot to convert my MPEG2 videos to XVID format. The problem is that where most of the videos are properly encoded, a few of them have audio video sync problem. Why does this happen and what can be done so that this doesnt happen.

The settings that I use are as follows…

Output Resolution : Auto Width
Output Audio Type : CBR MP3 128 Kbps
Output size : Approximately 10-12 MB per minute of video.

Please help.

Thank you.