Firefox is running very slow and when I type in field with drop down boxes, t information flashes but goes away adn i am unable to select fro them

Firefox is running very slow and when I type in field with drop down boxes, t information flashes but goes away and i am unable to select from them. Another thing notice is that in the box above as i type beyond the end it will go to the end then when i am typing and if there is any pause it scrolls back and i cannot see what I am typing. I have reset Firefox and opened in safe mode and continue to have this problem. I do not have this problem in internet explorer. I have Windows 7