Hi, hold down the Shift key when you start Firefox to start in Safe Mode. More - Diagnose Firefox issues using Troubleshoot Mode.

If it works in Safe Mode, disable any theme or extensions you have - 3-bar menu > Add-ons > Themes/Extensions and restart Firefox; then if it's OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some extensions.

If that doesn't help, open the Task Manager Ctrl + Shift + Esc and if Firefox is running, stop the application/end all processes.

Now do a Clean Reinstall; this means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location. With Firefox closed, use another browser to download Firefox from https://www.mozilla.org/en-US/firefox/all/ and save the file to somewhere convenient on your computer.

Now delete the Firefox installation folder which should be in one of the following locations -

C:\Program Files\Mozilla Firefox C:\Program Files (x86)\Mozilla Firefox

You can now double click the file you previously downloaded to install Firefox.

If it still won't start, disable your security program. If it starts, try updating your security and look at its settings for anything that might hook into browsers.

Finally, you can try creating a new Profile Profile Manager - Create, remove or switch Firefox profiles

If your question is resolved by this or another answer, please take a minute to let us know. Thank you!

https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved You may have corrupt xulstore.json or Localstore.rdf files.

Close Firefox. Open your file browser to this hidden location:

• Mac: *~/Library/Application Support/Firefox/Profiles
• Linux: *~/.mozilla/firefox/Profiles
• Windows: %AppData%\Mozilla\Firefox\Profiles
• *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles
• Windows XP: C:\Documents and Settings\<user>\Application Data
  \Mozilla\Firefox\Profiles\

Search for the above files. Then rename or delete them. Restart Firefox.

Sorry Fred McD I do not understand what I should do. How do I open my file browser (what is this?) to this hidden location (what location)

Hi, there are 2 things being discussed here. Fred would like you to go here :

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

or can Copy/Paste to run : %AppData%\Mozilla\Firefox\Profiles and it will take you to your Profile. Then follow Fred's url regarding the 2 files mentioned.

The other being discussed is do this but I would do the above to get a copy of your profile and save it just in case : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved.

Reinstall with Current Release Firefox 60.0.2 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

fyi for the future please backup :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

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

Sir, Thank you for your email. I have followed your instruction in connection with the profile then adopted Fred’s suggestions (22.06.18) with the following results. I tried to delete the Windows file %AppData%\Mozilla\Firefox\Profiles and C:\Users\Owner\Roaming\Mozilla\Firefox\Profiles and received the message: You require permission from Lenovo-PC (my computer name) to make changes to this file and as I do not know how to get such permission I was unable to complete that task. However I carried out Scribe’s instruction’s (22.06.18), started in safe mode which disabled two extension namely Trusteer Endpoint and Norton Vault. I enabled Norton Vault and Firefox starts correctly. I attempted to enable Trusteer Endpoint and received the message: IBM Security Report Another program on your computer installed an add on that may affect Your browser. Please review this add-on’s permission request and choose to enable or cancel (to leave disabled). I chose to leave Trusteer disabled and Firefox now works correctly. I understand the Trusteer will not work with Windows Edge and IBM are working on this, does this apply to Firefox also or do you know how I may install Trusteer on Firefox and leave it on Internet Explorer. Alternatively how may I disable Trusteer in Internet Explorer so that I may install it on Firefox to remove the conflict. Thank for your help. Derek Taylor

You should contact Trusteer support and ask questions. Also, make sure Trusteer is updated.