You might be better off making an imagine in the following manner:

Put your Flash header on the page, and take a screenshot of it, paste the screenshot into the Photoshop of your choice and make a wide and short image, that just covers the width from the left to the right behind the Flash header. Then, put that as background with repeat-y on it.

#headerDivision { background: url(../images/backgroundHeaderDivision.gif) repeat-y; }