hello LadyJoanne, please try to reset firefox by holding the shift key while you're launching the browser & then choose reset in the dialog that appears.

Refresh Firefox - reset add-ons and settings

Hello Philipp,

I've just tried to launch the browser while holding the shift key, but it crashed immediately as it did before, and the Firefox Safe Mode dialog didn't appear. I've also updated Windows and uninstalled then reinstalled Firefox, but neither of these actions worked either.

Can you bring up the Profile Manager to create a new profile?

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

These programs were flagged in your crash reports;

kernelbase.dll = Microsoft

ntdll.dll = Microsoft

Signature OOM

Total Virtual Memory 4294836224

Available Virtual Memory 4080644096

System Memory Use Percentage 41

Available Page File 6589435904

Available Physical Memory 4966453248

OOM Allocation Size 1959184400

Perform a System File Check to fix corrupted system files http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html

See if there are updates for your graphics drive drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

cor-el,

I did as you suggested and created a new profile and transferred my bookmarks and some of my applications into the new profile, and the new profile appears to be working perfectly, so I believe it was a corrupted file in my old profile that was causing the problem. I've scanned using Malwarebytes and McAfee Antivirus (although I haven't tried any of the others), and no viruses or malware was found.

Thanks very much for your help.

FredMcD,

I checked for updates for my graphics drive driver but there weren't any (although I had already updated them about a week ago, so there probably wouldn't be any more updates yet).

I performed a System File Check as described in the link you provided, and after the scan it stated that 'Windows Resource Protection found corrupt files and successfully repaired them'.

Many thanks for your help.

Glad to help.

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.