Custom Header Based on Category Again

I asked about this yesterday and someone sent me to: http://codex.wordpress.org/Conditional_Tags#A_Category_Page

I’m sorry to repeat myself, but that still didn’t help.

I’m very close. The code below is where I am, and what’s confusing is:
“About Us” header doesn’t work. It goes to the default header (header-home).
“Our Approach” header doesn’t work. It goes to the default header (header-home).
“Portfolio” header DOES work. It goes to the portfolio header.
All other pages go to the default header as they should (header-home).

<?php
if (is_category('About Us')){
include(TEMPLATEPATH.'/header-aboutus.php');}
elseif (is_category('Our Approach')){
include(TEMPLATEPATH.'/header-whyus.php');}
elseif (is_category('Portfolio')){
include(TEMPLATEPATH.'/header-portfolio.php');}
else {
include(TEMPLATEPATH.'/header-home.php');}
?>

Please…. I feel like I’m so close, and I really need to get this done. Any help would be highly appreciated.

Here’s the site if it would help.

http://bluegrassphotography.net/testwordpress/