An annoyance in Firefox, is anyone in the same boat?

Just a couple minutes ago this new empty bar appeared underneath my bookmark bar and above my tabs. It’s there when I don’t have any tabs open, too. It happens on every theme I try, including original. I’ve looked through my add-ons too see if it’s supposed to be a toolbar, but it’s not. I also looked in “customize” but nothing there either. Anyone else experiencing this problem? It’s quite annoying. Screen shot: http://img529.imageshack.us/my.php?image=emptybaryi1.png