Mysterious appearing top-border in custom blocks

I have been working on a custom theme for a news portal, based on the "Beginning" theme. The one problem I have run into, and not been able to solve, is a top border that appears in the custom blocks I create. You can see this in the header area of the site right now -- http://www.ucpa.us/ -- running across the background graphic and behind the site logo (below the drop-down menus and above the search window).

I have went through the CSS and PHP numerous times and cannot find where this errant top-border comes from. If you need to see any of the code, let me know and I'll post it. Once I have this working properly, I plan to create a generic version to upload here.

Henry Miles