Can't avoid black frame at start of .flv

I often need to convert to .flv for online delivery. But sometimes the screen for the link to the videopodcast shows black on the webpage. I've tried using about 5 frames of static image to begin the video; and sometimes it works. But others, even by using a full sec. of static image won't prevent the black screen from showing instead of the title image.
Has anyone have a solution? It will be much appreciated.

Alberto