After watching a youtube video in full-screen mode [f] or [F11] (in a window with about 20 concurrently running tabs of various other (non-video) things), the whole control interface area (address bar, menu bar, window header) disappears. This only affects the window that played the video, & although the other tabs areyet available through [Ctrl]+<hotkey>, all tabs in the wind lack the window/browser control interface. Firefox returns to normal after a re-opening of the browser. This disappearance does not resolve by just pressing the [Alt] key or by moving the mouse cursor to the top of the screen or by pressing [f] or [F11] to toggle full screen/normal. [F4], [Alt]+D, [Ctrl]+L, & [F6] are of no effect as URL input becomes unavailable (including no known access to "about:" features. [F12] does what it normally does (show webpage source code/elements). [F7] triggers caret browsing prompt. I did not bother with [F1], but all unmentioned F-keys were of no effect when pressed without combining with other keys. Perhaps it's a Win7 64-Bit issue, but I hope that you have a FireFox answer. Thanks in advance.