I've used both apps for years, but this is first install of Norton Security on my Windows 10 Pro (v 10.0.17763 build 17763). Firefox (v 74.0) immediately seized up with "Tab Crashes", and after closing would not reopen from the task bar.
In my first attempt, two Norton extensions were added to Firefox before the crash. Have since uninstalled Norton (re-activated Defender), un/re-installed Ffx, reinstalled Norton w/o extensions. Now Ffx tabs are not crashing, but Ffx still does not launch...the only way I can launch it is from the Norton window, so all my "home" tabs do not open.
Windows 10 Pro
Norton Autofix Results: 0 item(s)
Without Norton, Firefox works fine. Also running Office 365, Adobe Reader DC; no other known issues since installing Norton.