bg_header_bottom_left.png disappears when search results returned

The graphic bg_header_bottom_left.png, which is used as the default page header background grahic, is not served along with search results thereby causing my primary menu and search box to move all the way to the far left of the page. In fact all the background graphics and table colors have disappeared with the sole exception of the Navigation block. What is causing this and more importantly how can I fix this?