Twenty ten drop down menu unselectable

I’ve just added a submenu item to my main navigation. It appears when I rollover it but I can not select it. When I drag my mouse down to do so the submenu item disappears.

I’ve tried deactivating all plugins and it had no effect.

I’ve inspected the element using firebug to see if I could identify what might be causing the problem and the HTML code is actually grayed out.

Here’s the site link: marymaru.com. The problem item is under the Portfolio navigation.

Thanks for any suggestions.