Actually when I apply any change in the image (size, position, effects) everything is fine. The problem appears when I just move the video in the timetable. I also tried to just upper field and both fields but that didn’t change anything.
When I do the rendering in .avi or something else there the video is clear (like the source or the preview screen when I captured).
Strange because I had tried the demo of CS4 on the same configuration which worked.