Start your Computer in safe mode with networking. Then start Firefox. Try Safe web sites. Is the problem still there?

Starting The Computer In Safe Mode;
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Booted Windows safe mode with networking, no change: Firefox still froze as soon as I tried to open options without even trying to visit any web sites. A tab opens for the options but FF hangs without displaying anything.

Some more data to add to the mystery: (1) I logged into the rarely-used admin account on this laptop and Firefox options worked just fine (2) Logged back into my own account, ran firefox -p to create a brand new profile and used it: FF still freezes So something about my Windows account but not others in both in normal Windows mode and Windows safe mode would seem to be responsible but I can't guess what...

Shut down Firefox. Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Right click on Firefox.exe and select Properties. Now select Compatibility. Turn Off Run This Program In Compatibility Mode, and Run This Program As An Administrator.

Do the same for any Firefox shortcuts you have. Now restart Firefox.

(a) enabling compatibility mode alone does not fix the problem (b) setting "run as administrator" using the Advanced button on the Shortcut properties tab does work whether compatibility is enabled or not but of course this defeats the security of running my user account without admin privileges.

Only this laptop has the problem: on my other Windows 7 PC Firefox runs just fine without admin privileges. Is there any more troubleshooting I can do to provide more info? I am willing to use one of the Microsoft sysinternals tools if given directions as to what to run etc. to provide additional info...

FredMcD said

Turn Off Run This Program In Compatibility Mode, and Run This Program As An Administrator.

What security programs are on the sick computer? Disable them for a test.

Laptop is using Microsoft Security Essentials, same as my other PCs where FF works fine. Disabled MSSE and Firefox still froze as soon as I tried to open options.

How are you starting Firefox? What is your home page?

What I want you to do now is to create a new, blank user profile. Make no changes in this profile. All we want to do is see if it works.

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Windows: 32-bit C:\Program Files\Mozilla Firefox\firefox.exe -p 64-bit C:\Program Files (x86)\Mozilla Firefox\firefox.exe -p Mac: Navigate to /Applications/Utilities. Open the Terminal application. In the Terminal application, enter the following: /Applications/Firefox.app/Contents/MacOS/firefox-bin -p Linux: In Terminal run: firefox –P For users who have one or more builds from mozilla.org this will not work. It would be best to have the full path so if you had placed the untared contents in a folder in /home it would be /home/<username>/foldername/firefox/firefox –P An easy way would be not to do it in a terminal but in say a launcher since you have to point it to the firefox script in Firefox folder you can then add –P on end. You can also have the exact "profilename" after the -P so Firefox will start with that Profile.

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

I've already tried both "Refresh Firefox" and creating a clean new profile, still freezes. I have the default FF home page. Although FF works for general browsing if I do any of the things listed in my original question FF freezes 100% of the time. Just launching FF and clicking the Options menu choice will hang. I also can't export my bookmarks which had me freaked until I tried setting up Sync which let me get my bookmarks into FF on another PC although I am having to slowly clean up the rather messy merger.

• 1 Download Firefox Full Installer For All languages And Systems {web link}
• 2 Uninstall Firefox from your computer {web link}
  DO NOT remove your profiles.
• 3 After, reboot the computer. Then run the full installer.

This might be a long shot, but have you updated your drivers recently?

• Upgrade your graphics drivers to use hardware acceleration and WebGL

Also I did not see what happened if you disabled plugins (all the ones listed under adobe and Office plugins)

Has anyone suggested CCleaner?

(a) complete uninstall and deletion of Program Files folder and reinstall using the full installer did not change anything

(b) @guigs2: yes, I've updated graphics drivers to no avail. Since options freeze FF I haven't directly been able to disable hardware acceleration but I was able to set up Sync with Firefox on another PC and disable hardware acceleration there so that may have been picked up on the problem laptop. I've done a Firefox refresh to disable all plugins and that doesn't help either. I was already using CCleaner when the trouble started so I tried uninstalling CCleaner which didn't change anything.

Can anyone tell me what was the last Windows FF version that had the standard tabbed Windows dialog for the preferences instead of the pretty new UI? It seems like that was the last time when FF worked fine for me, I'd like to go back to whatever that release was and give it a try.

I downloaded and installed the 64-bit Firefox Developer Edition (40.0a2), using Sync to get settings from my 32-bit profile. Options and file downloads work, hurray! -- Saturday 6/6: so far so good, the only extensions I use are Adblock Plus and Flashblock and both seem to work fine. I have <not> enabled the multi-process option.

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.