What version were you using before? Did you make any changes after the update?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Keep this just in case;

Install an older version of Firefox {web link} Be sure to read everything here.

If you still want to downgrade, look under "I still want to downgrade" Click the Directory of other versions and languages link Look for the directory of the version that you want. But remember that old versions may have security issues.

More like something is getting triggered under the right conditions. The PSU load, drivers, run level software, bad memory etc.

Thanks for both of you responding. What I found on the Firefox sight was a problem resolution that said if you are experiencing problems with the new update since I was already on 51.0.0 is to completely remove the Firefox from your system. Then go to the Mozilla.org official site and download a fresh copy of the update. I did this last night and everything so far seems to be working better than I had before, so something is good. Hope someone else can use this same info with the same problem. You can always ask me if need!