Help me please, fisrt sorry my english, when I use slow motion (velocity envelope) or just dragging mouse with control key, the mpeg created shakes , flicker.. what I 'm doing wrong..
The information you left is too vague. Slow motion shouldn't cause these problems. Sometimes cropping and enlarging or reverse interlacing can do this and possible a number of other things. You need to describe, as best as you can, exactly what steps you've taken to get to the mpeg stage. If you used any other programs besides vegas, in the process. The more detail, the better we can answer.
Again, I have to guess. Try capturing with Vegas via firewire. You may be reversing the field order when you use a different program. That happened with me and using Ulead products a while back. Or try reversing your .avis field order when rendering to mpeg, (go to custom window then the video tab and look at field order. Bottom first is normal, but depending on what your source is, you may need top first.)