When I start Firefox ''' Power up, use Firefox , access net no problems. I close session with X in top right corner, I cannot restart Firefox using desktop icon. I try to power the computer down. Message comes up that I have to quit Firefox because it is running and will not allow the computer to be shut down. I click the Quit Firefox tab , computer shuts down. I can then access the net through startup from the desktop icon and the process repeats itself. '''