Transparency problem with CSS and blogs MU

I have created a child style for my website and have been playing around with the style of blogs.mu.

I have had great success by using firebug and just adding the div id's and classes to my child style.css and over riding the parent theme with !important.

I would like to color the background of #intro-content and #wrapper and then give the internal divs a white background.

I was hoping this would enable me to have a black border with the two internal divs
'#intro-content'
'#cbox'
having a white background with my content on, this does not happen.

What is strange is that if I use firebug to temporarily edit the two divs in my browser.
background-color: transparent;
and change it to
background-color:black; I get the desired result.

What appears to be happening is that background color is set to transparent in bp-default.css, thus overriding my custom style sheet, even with !important.

Is there a way in which I can overide bp-default, to get the changes I desire?.

~sorry for the long post
Andy