http://208.100.51.162/ <-- site URL

You'll know it when you see it.

I can't seem to get it to go away. I've been debugging at it forever.

Note: its running Thesis / Wordpress

1 - you have an unclosed <a> tag inside your H1
2 - You're re-using id="header" and ID's MUST be unique on page. If you must re-use css rules, make it a class instead.

Reduce the amount of padding on the <a> inside your menu, the list is too wide to fit into the available space.