The headerTop div isn't tall enough to fit the (3) div back-ground images without a 10px overlap - this is causing the darker strip in the drop-shadow effect (the drop shadow being semi-transparent).
Increase the height of the headerTop div and position its bhs_logo.png background image correctly on the y-coordinate:
#outerWrapper #headerBackground #headerTop {
background-image: url(../BHS2_images/bhs_logo.png);
background-position: center 23px; /* position the y-coordinate */
background-repeat: no-repeat;
height: 178px; /* increase from 168px */
}
This should fix the header bit.