in fact, ive got no idea why this may happen, except firefox being damaged in certain way (probably by using it too frequently, it simply wants to retire in honour), but obviously there are no system- or hardware-problems on your CPU (why should IE run that quickly if you had some...) and as it seems to be a firefox-problem i would recommend to deinstall and reinstall, maybe even an older version of firefox.
(ocultar) Si deseas encontrar un adversario de parecido nivel de juego al tuyo, echa un vistazo en la página de Clasificaciones del tipo de juego que quieres y busca a uno con un BKR similar. (pauloaguia) (mostrar todos los consejos)