Hmmm, why do you have a tab up in the title bar and a maximize window icon? Normally, the the tab bar appears below the Firefox button if the window is not maximized. Are you using any add-ons that affect the toolbar layout?

Its just how my windows theme is. The restore/maximize icons always display the same picture. I assure you the window is maximized. When its not, the grey bar is much wider and fills up most of where the tabs are.

Also, I don't have any add-ons that effect the layout. I tried safe-mode with themes/addons disabled and the bar is still there

Well, when tabs are in the title bar, the tab bar background changes to a gradient fill that appears to create a gap at the bottom:

background-image: -moz-linear-gradient(center bottom , rgba(26, 26, 26, 0.4) 1px, transparent 1px), -moz-linear-gradient(rgba(128, 128, 128, 0), activecaption 85%);

background-image: -moz-linear-gradient(center bottom , rgba(26, 26, 26, 0.4) 1px, transparent 1px), -moz-linear-gradient(rgba(128, 128, 128, 0), inactivecaption 85%);

It's a little too late here to experiment with a fix, but hopefully another forum contributor will be able to recommend a solution.

(When the window is not maximized, the background of the tab bar is transparent.)

The menu bar (file/view/etc), when not hidden, is the same color as this mysterious white bar, maximized or not http://i49.tinypic.com/8w9kjd.png

Maybe try a theme.

• Firefox 3 Aero theme for Firefox 4+: https://addons.mozilla.org/firefox/addon/firefox-3-aero-theme-for-fi/