Message says that Firefox needs to close. It does not appear to be running even when the "Taskmaster" (Ctrl-alt-delete) is displayed. The message says to close Firefox or reboot my computer. It happens constantly, even though I have closed Firefox, already. It appears to happen most often when I reach a page that refuses to respond to any mouse clicks, although, I can close the page (x). I, then, I cannot open Firefox until I reboot.