I asked this a month ago, but no one could help, so I try again.

I have converted some Mpeg files to DivX using Virtualdub and this guide:
https://www.videohelp.com/avi2divx.htm

Everything turns out fine expect that the first 10 seconds are completely pixelated and distorted. The rest of the clip is fine. I tried many files and it happened with all of them and it was only the first 10 seconds or thereabouts.

Anyone know why?