[SOLVED] Fill background of custom menu

Greetings,

I'm building a new version of my website over at robotsandoctopuses.com, and I'm playing around with centering the menus.

I have the following CSS insert:

div#menu1 {
background: #CDC9C9;
border: solid #CDC9C9;
}

This used to fill out the menu completely when I was just using the basic Page / Category menus.

When I switched to using a custom menu, it seems like the CSS insert doesn't fill out the background.

Anyone know what I should change the insert to, to fix this?