I don't think that helps.
The FAQ says to add the hex value in the flash object in the index.html file. The hex value is already there, and when I launch index.html in the browser, the background is white.
But I don't use that page index.html in my site.
What I do is I embed the flash file viewer.swf in my own html page. When i preview it in the browser, the background of viewer.swf is always gray and that is what I can't change. I thought it can be changed when you build the file, not in the "post-production process".
This is the first time I've responded to a query so here goes. I was having the same problem. I have created a 'gallery.html' page that has the viewer in a div with the id "flashcontent". Within that div is this line of code:
var fo = new SWFObject("viewer.swf", "viewer", "100%", "100%", "8", "#000000");
It was changing the hex value in this line from #181818 to #000000 that created a black background on my 'gallery' page. Altering the CSS values for flashcontent did nothing.
Hope this helps.