Try this : https://support.mozilla.org/en-US/kb/firefox-keeps-crashing-startup and https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems?redirectlocale=en-US&redirectslug=Troubleshooting+extensions+and+themes

Please let us know if this solved your issue or if need further assistance.

Try to start Firefox in Safe Mode to see if that works.

• Windows: hold down the Shift key while starting Firefox
• Mac: hold down the Options key while starting Firefox

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Thank you, cor-el - I have tried the safe mode and it doesn't work either. Thank you, Pkshadow, too for your link. I just got lost in it.. I am not a geek - isn't there a simpler answer for a 'simpler' computer user ?!? It is now 3 days of not being able to use my Firefox because of this most unfortunate update ! At least can somebody tell me how can I get back the version of before this unfortunate update ? With many thanks in advance, G.

What security software do you have?

It is possible that your firewall or other security software blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program. Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access to install for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/en-US/kb/server-not-found-connection-problem
• https://support.mozilla.org/en-US/kb/Firewalls
• https://support.mozilla.org/en-US/kb/fix-problems-connecting-websites-after-updating

Hi cor-el, thank you for the new links. The security software is Comodo (Windows Firewall is turned off). I have checked and made sure that Firefox is allowed by Comodo but it is still dead ! I also tried Safe Mode again, then Refreshing, then Uninstalling & re-Downloading but my Firefox is still dead ! I found this through the Troubleshooting page - maybe it gives you a clue ?

Decision Log

HW_COMPOSITING

blocked by runtime: Acceleration blocked by safe-mode

D3D11_COMPOSITING

unavailable by default: Hardware compositing is disabled

DIRECT2D

unavailable by default: Direct2D requires Direct3D 11 compositing

D3D11_HW_ANGLE

unavailable by default: D3D11 compositing is disabled

disabled by env: D3D11 compositing is disabled

GPU_PROCESS

blocked by runtime: Safe-mode is enabled

WEBRENDER

opt-in by default: WebRender is an opt-in feature

unavailable by runtime: ANGLE is disabled

Those messages indicate that you had started Firefox in Safe Mode.

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Did you manage to start Firefox in Safe Mode, but not in regular mode?

Dear cor-el, thank you for your kind help. Obviously, the 56.0.1 hasn't been well thought and executed. Until Mozilla finds 'a patch' to resolve the bug I decided (after 5 days spending precious time trying the impossible !) to 'defect' to Chrome.. It's a pity because I used to enjoy the Firefox. Once again, with many thanks for your kind attempts to helping me.

Faced the same crash after automatic update to 56.0.1

Unable to connect any address, even localhost - just new empty tabs added. Full remove regedit.exe cleaning, installation of new 56.0 and elder versions is not helped.

Hi Chuckie- and Confused5:

The Firefox 56.0.1 updater switches users with 64-bit Windows 7/8/8.1/10 from the traditional 32-bit version of Windows to the 64-bit version. This seems to have some odd side effects on some systems that we haven't always been able to sort out.

In some cases, the issues can be resolved by the workaround of reinstalling 32-bit Firefox. That may not be a permanent fix, but if you did want to try that, see: How to opt out of 32-bit Firefox migration to 64-bit.