I can not click 'close tabs' i cannot click 'cancel' and i cannot even see the 'Help' option at the top of the screen. Its just a black screen, the 'close tabs' pop up and the Mac apple on the top bar of the computer that also says firefox but none of the other options are there. (File Edit View History etc. etc...) Also i can't force the app to quit and the computer says it can't restart or shut down until the app is closed.