I love Firefox and I am much grieved to have had to stop using it and return to IE. I went and updated with the latest model, over my existing installation, and that did not cure the problem. I'm not doing anything differently than I ever did and when it started I had not recently installed any new extensions, themes, etc.
It simply goes away, sometimes when I'm reading a page, maybe I'll just move my mouse pointer a little, to get it out of the way and clunk! Sometimes I'm not even at the computer because I've got up from my chair and I'll turn around and my browser is gone. It'll shut down when I'm in the middle of a download, not always, just sometimes. No apparent reason for this but now I cannot trust it to stay up anymore. Yesterday I clicked on a video at youtube - the play button - and down it went!
I am a newbie, though quite old, so I don't know here to look for the problem, other than the usual, like check for spyware or virus. I haven't found any. Should I simply uninstall every trace of this browser and start over? I go to a lot of news sites all over the world, and software forums also; it is possible that I got nabbed by something but I cannot imagine what. Can anyone advise me what to do?