I've seen this happen twice on two different machines (Both Mac), so time to file the bug. Very intermittent, but is happening. When running FFx5beta on the run up to the official launch, I opened the browser one morning an was unable to click and activate any of the Menu Bar options (Apple, Firefox, File, Edit etc.). Other programs running on the machine accessed these menu items just fine, FFx was the only application locking these out. I force quit and restarted and everything was back to normal so let it slide until... This Morning, my coworker's machine (Also Mac, FFx 5.0) demonstrated the same issue, unresponsive Menu Bar. I did not attempt to access these menus via keyboard (wish I would have). Starting the application after a System Sleep mode seems to play a part. Haven't yet seen this while running Aurora. Adding this bug for tracking. Work around is to force quit, restart.