hi steve, thanks for providing a crash report id. we have seen quite a number of similar reports about this issue in the last hours and this issue is likely caused by your symantec security software that is hooking into firefox (probably through a program/signature update done by them). other users reported that updating firefox in this situation helped with the crashes. you can download & install the latest firefox from https://download.mozilla.org/?product=firefox-48.0.2-sha1&os=win&lang=en-US

Thank you Phillip. This answer solved the problem.

My only concern is that when I went online to download a new version of Firefox (last night when this occurred), the latest version I saw was 43. The version I just installed is 48. Just wondering why I wasn't presented with 48 last night.

Anyway, problem solved!

thanks for your feedback - unfortunately we have to serve 43.0.1 to xp and vista users on the normal download page (due to a different code-signing issue that some versions of those old operating systems are no longer compatible with). that's why i gave you the particular link for 48.0.2

My Win 10 Pro 64bit system crashed and when I got it going again, Firefox would not open. Uninstalled, removed Firefox Folder and Reionstalled - Still wont start with Crash Reporter coming upd. Have sent reports but no answers.

@Nasho23: please open a new question for issue, since it won't receive any attention at the bottom of an already solved thread: https://support.mozilla.org/questions/new