I am using Firefox on Mac - I usually minimize instead of closing - It has started making a TAPPING NOISE I thought it was my computer - but It now has happened to 3 different computers and one is brand new - T T T T TTT , I have narrowed it down to Firefox, when I minimize it will do it, then opened and it stopped and min. then start, repeeat - now it does the TTTTT all the time with it open or minimized. What is going on?