I'm seeing this problem too, and don't know how to fix it...
I tried setting up my skin's CSS rules like this:
body {background-color:Black;}
body * {background-color:White;}
But that did not help; the FCKEditor's background stayed black. :(
Next, I tried setting up my skin's CSS like this:
body {background-color:White}
.blackbackround {background-color:Black; width:100%}
And wrapped the entire content of the skin .ascx file in a div which I set class="blackbackground" like so:
body
div class=blackbackground
[skin code]
/div
/body
This sortof worked, but doesn't work very well if the viewpane height is taller than the content of the div, because then you get a white area at the bottom of the page where the div ends and the body's background color shows.
Looking for a better/permanent fix... I guess avoid black background sites until fixed.