On Mac, two jpg's whose color should match do not

Question

So I'm designing a myspace page and I have two images, one is a repeating bg image, and another is an image which loads on a layer above it, which acts as a header/masthead. For some reason, on Macs only, and only in the browser (tested in safari and ff), the masthead renders slightly darker than the repeating bg image, creating this color inconsistency. The block that extends up behind the album artwork is a solid box made with css which blocks some of myspace's standard content. It actually renders as the proper color, blending in well with the bottom portion of this image, which is the repeating part of the background, but becomes noticeable as it extends up, over the masthead, which is darker than it should be. Both images where created in GIMP and saved as jpg's using, as far as i can tell, the same settings.

Here's the pic of what is going on:

Screenshot - Click Me!!!

Here is the code which controls this part of the design.

<div class="masthead"><span></span></div>

.masthead {width: 1600px; 
    height: 1940px; 
    background-image:url(http://www.sourtricks.com/myspace/bdww/myspace_bg09.jpg); 
    position: absolute; 
    margin-left: -800px; 
    left: 50%; top: 0px; 
    z-index: -1; 
    overflow-x: hidden;}

body.bodyContent{
    margin: 0 !important;
    padding: 0 !important;
    background-color: 000000 !important;
    font-size: 1px;
    background-image: url(http://www.sourtricks.com/myspace/bdww/bg_repeat05.jpg);
    background-position: center bottom;
    _background-position: right bottom;
    background-attachment: scroll;
    background-repeat: repeat-y;
    z-index: -2;
    overflow-x: hidden;
    font-family: arial, sans-serif !important;
}

Any help would be much, much, much appreciated. Thanks for your time, Tim

Answer 1

mypace_bg09.jpg has a colour profile set: sRGB IEC61966-2.1 - bg_repeat05.jpg does not.

I think this makes up for the difference. You should handle that equally in both images.