Many have reported issues using the 64bit Firefox. Install the 32bit version from; Download Firefox For All languages And Systems {web link}

Tried the 32-bit version but I get the same problem.

Just to be sure; You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

Yeah, tried several and ran CCleaner and Glary's through the registry as well but still no luck.

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

Can’t try to start Firefox in safe mode because it won’t start at all so I can’t select the option. I’ve already tried booting the PC in safe mode w/ network but I get the same error.

I called for more help.

Refreshing Firefox {web link} is a LAST RESORT ! !

Refreshing Firefox -- easily fix most problems

If you're having problems with Firefox, refreshing it can help. The refresh feature fixes many issues by restoring Firefox to its factory default state while saving your essential information like bookmarks and open tabs. Everything else, like user settings and add-ons, are removed. Note: Refresh saves your old profile to the desktop in a folder called Old Firefox.

Already tried that. Didn’t work.

Did a system restore to a session prior to the last two Windows updates I completed and that's got it working again. I'm not sure which update was the one that caused it to stop.

Does your computer have the Symantec Endpoint Security program? This would usually only be installed in a business environment. Apparently if its rule against browsers downloading executable files is enabled, Firefox breaks in the way you mentioned (or so it sounds to me): https://support.mozilla.org/questions/1264492

Nope. It’s got Avast! Installed.

Odd. I rebooted my PC this morning and the same issue is occuring even though I haven't re-installed the Windows updates so it wasn't them that was causing the issue.

I'm at a loss.

Hey did you sort the issue out? I have the same problem. I unintstalled AVG Free from my computer and Firefox works fine but now Im without an anti virus software. can someone please help? oh my issues started on friday.

Nope. Mine’s still buggered.

Try uninstalling Avast on your machine and see if this works.

Yes, uninstalling Avast and then reinstalling Firefox seems to work.

Hey this might help, I installed Firefox 67.0.4 which was the previous version. This works fine with AVG. I have switched off auto updates for Firefox. This way I can use Firefox and AVG.

There seems to be a conflict with the new version of Firefox and AVG/Avast. I hope someone can shed some light on this! Can anyone help???

Thanks

Hi, it was already reported to avast forum (https://forum.avast.com/?topic=228355.0) but we are not able to induce it. Clean firefox 68 and avast 19.6 seems to work without conflict. May I ask you which extensions do you use ?

vaclav.pich said

May I ask you which extensions do you use ?

Type about:support in the address bar and press Enter. Under the main banner, press the button; Copy Text To Clipboard.. Now in the Reply Box on the forum page, do a right-click in the box and select Paste.

This will show us your system details. No Personal Information Is Collected.

Till we find a reason why firefox cant start we decided to disable avast parts which may interact with browser. Thank you for report !