Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

You can check for issues caused by a corrupted or incomplete Visual C++ installation that is missing runtime components (Redistributable Packages) required by Firefox, especially VCRUNTIME140_1.dll.

See "Visual Studio 2015, 2017, 2019, and 2022":

• https://docs.microsoft.com/en-US/cpp/windows/latest-supported-vc-redist
• https://aka.ms/vs/17/release/vc_redist.x64.exe
• https://aka.ms/vs/17/release/vc_redist.x86.exe

You may also have to install the Visual Studio 2013 Redistributable Package. You need to reboot the computer.

(edited to include the 2022 update)

After reading the initial article you posted, I installed both vc_redist*.exe's. This changed the behavior of FF 97 slightly, in that now while the pages are not loading, they do display the loading animation bouncing dot in the tabs. Previously they were just still and blank.

Also, now Ctrl + B reliably toggles the bookmarks sidebar again, tho only on new tabs, not on "forever not loading" pages.

While my system is 64 bit, the article indicated it was the target environment determined in the *.exe compilation one had to match, so my initial install of x64.exe did nothing, but the x86.exe changed the tab loading animation behavior as described above.

BTW, while your links to the redistributables had /16/ in the URL, the article had /17/, and that is what I used since that section See "Visual Studio 2015, 2017 and 2019" listed them thus. After install, my versions are listed as: PS C:\windows\system32> dir vcruntime140*.dll

   Directory: C:\windows\system32

Mode LastWriteTime Length Name

-a---- 1/6/2022 9:26 PM 97144 vcruntime140.dll -a---- 1/6/2022 9:26 PM 37256 vcruntime140_1.dll

The FF 97 update is working fine on 2 old pcs & 1 vm.

I tried copying the vcruntime files from working machines to my main machine, which is the newest & cleanest of any of them. Same results. FF eventually crashes while not loading these pages.

Other than being much newer, i.e.: Processor 11th Gen Intel(R) Core(TM) i7-11800H @ 2.30GHz, 2304 Mhz, 8 Core(s), 16 Logical Processor(s) Video NVIDIA RTX A3000 Laptop GPU

...these are all Win 10, some Home, some Pro, most at 21H2 with pretty much the same batch of apps/setup.

As a user of FF for as long as it's been around, and going back to the Netscape beta days, I am completely enmeshed in it's usage. Not being able to run v97 on my main workstation is terrible. Reverting to v96 to remain functional, but would like to help surface whatever is going on here. In theory this well specced fresh machine should be most up to date and compliant. Not even being able to load about:config to test (other possible fixes to recent similar problems like the http3 thing) is rough. Never seen a code push like this.

Should I be seeking to file a bug report, and/or gather more system data to do so?

I tried copying the vcruntime files from working machines . . . .

The files need to be installed so the computer knows where to find them. See: https://support.mozilla.org/en-US/questions/1367313#answer-1482082

I chased down the root cause of my problem. It was WebRoot. For some reason, the v97 upgrade worked with most of our users, but not for a couple others. After consulting with WebRoot, they advised this was a known issue. The fix was to remove and reinstalled the WebRoot application.

A couple of ours self-resolved, but we resorted to uninstalling/reinstalling one.

The quickest way to troubleshoot this for us was to temporarily turn off WebRoot protection. Firefox worked fine with it off (and Defender enabled in substitution). Turn WebRoot back on and it was hosed.

I chased down the root cause of my problem. It was WebRoot. For some reason, the v97 upgrade worked with most of our users, but not for a couple others. After consulting with WebRoot, they advised this was a known issue. The fix was to remove and reinstalled the WebRoot application.

Thank you for this update. If removing and reinstalling WebRoot resolves the issue, I wonder whether that means either (A) WebRoot has issued an update or (B) during reinstallation, WebRoot is configuring slightly differently in light of what it has found on the system. Either way, this is very helpful to know.

Thanks so much to "bg07901"! Uninstalling then reinstalling WebRoot fixed the issue!

I am so relieved and pleased to have FF latest install back and running :)

I always disable the WebRoot extension in FF, assumed it couldn't interfere. Had actually tried disabling WebRoot & it's component "Web Shield" early in the troubleshooting process, which did not affect the issue at all. FF was still broken w/ WebRoot disabled.

My older machine w/ WebRoot & FF in basically the same config was not affected by this issue (FF profiles all synced amongst machines).

https://www.mozilla.org/firefox/97.0.1/releasenotes/

Fixed Works around problems with WebRoot SecureAnywhere antivirus rendering Firefox unusable in some situations