I've been using Firefox for ever! It has been great until recently I had to close it down a few times because of it freezing and now it says it crashed whenever I open it. I've had to switch to IE and it's really hard cause I'm not use to it...I miss my firefox.. 
That happens to me occasionally, try going into your task manager and ending the firefox process(es) (however many there are). That usually works for me.
I almost always use Firefox, I avoid IE whenever possible, and only recently downloaded Chrome when a website I use for school was having 'issues' with firefox.
Of the three, I'd say that:
Chrome is the fastest, and second most secure.
Firefox is the second fastest and most secure.
And Internet Explorer is the slowest and the least secure, plus, it gives me a headache.
