Something Wicked This Way Comes

I have been having some weird behavior with Firefox.  Using speedof.me, I was getting okay data rates (likr 4Mbps down, 2 Mbps up) but keystrokes in my browser had a noticeable echo problem.  I reset Firefox to its defaults and the slow response went away and 9.98 Mbps down, 2.89 Mbps up.