grey frames when converting mp4 to xvid

[Snowcrystal]

Hi,

I've got a problem with converting mp4 to xvid. I've done a batch conversion of mp4toxvid with avisynth 2.5 and virtualdub 1.6.17. When checking the result most xvid files have some problems at the beginning. When playing it starts flickering grey frames mixed with normal frames very quick for a few seconds and then it plays normally. I've converted a few again, this time seperately but it still has some grey frames at the beginning though it's less this time.
When I play the original mp4 files there isn't any problem with it.
I use the cccp codec pack and xvid to convert them.
So what could be the problem?

[celtic_druid]

Some info here: http://forum.doom9.org/showthread.php?t=116947&highlight=grey+frames

[Snowcrystal]

Thank you so much. I couldn't find it with google.
I've installed an older version of avisynth and no more grey frames now.