Picture Alignment Problem

I have a new WP install and replaced the header image in my custom template with another one of the same size (1200×300). Unfortunately, it seems like about 1/2″ on the left/right of the image are repeated. Basically, a 1/2″ chunk was copied from the right side of the image and placed on the left, and vice versa.

I don’t see any reason why this would happen, does anyone else have a guess? My URL is https://trentscott.com — it’s the main image at the top.

Thanks in advance : )

Here’s the relevant CSS for the theme:

body {

	/*:Background image*/

	background-image:url(images/background/fat_lines.gif);

}

#header_image {

	/*:Header height*/

	padding-top:200px;

	/*:Header image*/

	background-image:url(images/headers/740210_63353419.jpg);

	/*:Header image alignment*/

	background-position:center;

}