DivX sound never stays in sync

I have been converting movies to VCD for a while now, using avi’s xvid, mpeg files.
I am having problems with DivX encoded films.
The sound never stays in sync.
I’ve tried extracting the audio using virtual dub, along with a host of other things, but even when the first 10 minutes of film look OK, the audio still strays as the film goes on.
I haven’t a clue why...?
Does anyone in here know

(I have been having the same problem although i cant say it happeneds to all of them.
What i have been told is that when your decrypting the movie you stick it on IFO mode then before clicking decrypt you go into them boxes underneath the one with the video files in it and go to the one on the left and uncheck the first box.
but be careful you only need to do this to the ones that are out of sync and not all files
from what i can understand of it when divx is converting it goes through every single frame i the movie and if it seens a long strech of a black screen then the audio will no begin there it wont actually start till it see’s a key video frame bit of a bummer really but what can you do