Two things to try;

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.

Install both 32-bit and 64-bit "Visual Studio 2015, 2017 and 2019" downloads, (x86: vc_redist.x86.exe and x64: vc_redist.x64.exe) from https://support.microsoft.com/help/2977003/the-latest-supported-visual-c-downloads

You may not need the latter (32-bit version) if you use 64-bit Firefox. You may have to reboot the computer. ++++++++++++++++++++++++++++++++++++++++++++++ In another thread, a user reported that a recent update of Malwarebytes Anti-Exploit (version 415) may be causing symptoms similar to the VC Runtime problem. If you have MBAE, it should have a setting to exempt Firefox. You could test whether that makes any difference.

Thanks a lot!

Glad to help. Safe Surfing.

Hi again, the reason I put this question here is that it might be related.

Now everything works (technically it does) but Firefox has become extremely slow. It takes very long time to navigate or even update a page (for example if i read my gmail within firefox).

• Network connection is good and if I use other programs needing a connection it works fine. If I use Edge och Chrome it also works fast. Firefox is both fast and good so it should not be this slow and I do not understand why.

• I also checked on my old computer and there it works fast and stable as I'm used to.

The only thing I can think of is that this has some kind of connections to all the installed packages (see attached picture). Can this be the case or is there anything else I can try?

(We are here talking about having to wait 5-10 seconds just for Firefox to follow my mousepointer when moving it over my bookmarks to give one example of how slow it have gotten, I.e it is now so slow that I can not use it although it tecnhically works).

I have tried to restart the computer, was hoping that some process have just looked itself but the solution was not that easy.

BR/Fredrik

Looks like you have many versions of the same programs. I don't want to tell you to do anything because I am not sure. I called for more help.

Thanks for helping out.

I did a complete reinstallation of Firefox (after which I did not remember my old password, did a reset of password and ended up in having ALL of my bookmarks lost so now I will need to try to find them on another laptop that is offline).

Anyhow, this accident means that I can now add to the information that even although all bookmarks and add-ons are gone Firefox is still extremely slow. I have also look in Firefox internal task manager (same here, after klicking at "tools" and moving the cursor down I had to wait 7-8 seconds until I could click browser toool) and nothing there seems to take resources although windows itself shows as if I had nine instances of firefox (and I only have one and i only have one open tab which is the tab where I am writing this message).

Hi (again), If this post does not help please just ignore it but there turned out to be another trouble (which says me nothing but might be of help in finding the issue).

When I tried to see this page: https://support.office.com/article/a7616fe0-46f0-4e05-9338-921a2d905ed5 it turned out to be impossible from my Firefox so I had to view it from Edge instead. To me more precise I got the following error-message: "Error code: MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING"

Sorry, current forum security sometimes delays the posting of messages.

Fredrik465 said; When I tried to see this page: https://support.office.com/article/a7616fe0-46f0-4e05-9338-921a2d905ed5 "Error code: MOZILLA_PKIX_ERROR_OCSP_RESPONSE_FOR_CERT_MISSING"

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-firefox-did-not-connect

https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors

What do the security warning codes mean

Hi, and thanks for the input.

So currently there are (was) 3 problems. And the showstopper here is nr.1

1. Firefox has since it started to work (after installing the Visual C++) become so slow that it is impossible to use (menues etc are so slow in response that it is practially impossible to use, just klicking "bookmarks->manage bookmarks->import and backup" takes all in all 45-50 secons of waiting on a fast computer with no load). I can just hope that @FredMcD get some answers regarding all versions of Visual C++ and that it will help so I can start using the app again.

2. The lost bookmarks (was able to solve this by booting my other computer in flight mode and backup all bookmarks to a file before going online and then restore them)

3. Problem that arised with not being able to open certain webpages I have not run into any other problems with webpages not loading so I guess and is using windows defender for AV. Guess I can wait with this one until I see of there is some solution to the unresponsiveness because otherwise I won't be able to use Firefox anyway.

3. Problem that arised with not being able to open certain webpages

Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

Make sure you are not blocking content.

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop also see https://blog.mozilla.org/security/2021/03/23/introducing-smartblock/

https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

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

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}

On my old computer i only have one instance of visual c++ framework

On my old computer i only have one instance of visual c++ framework

I suggest you ask here; https://support.microsoft.com

http://answers.microsoft.com/en-US/windows/forum/windows_10

Hi (again). So bookmarks are back and I can open all links again. I wrote down all Visual C++ installations and by chance removed all but the newest 64 bit version.

But, I still have the strange situation with Firefox being extremely slow. It's not the connection or downloading that is slow but Firefox itself. Have tried the "refresh" function and also made total reinstallation by first removing everything with Revo-ununstaller.

Nothing helps, and the "slowness" is still as extreme as described above. So any input regarding if there is a solution or anything more I can try before givving up would be appreciated.

Boot the computer in Windows Safe mode with network support to see if that has effect in case security software is causing problems.

• https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/

Hi, I'm runing windows 11 and after rebooting into "Safe mode with networking" there are no network. I guess I can find a soltion to that tomorrow.

In the meantime I can add some facts and things ITwo things I have tried:

• Using Edge or Chrome on the same computer => They work fine
• Using my older computer (that has same verison of the OS and also same version of Firefox). On the old computer Firefox works flawless.

I'm not using any other antivirus than windows built in defender.

. . . and after rebooting into "Safe mode with networking" there are no network.

WiFi is not loaded using the computer's Safe Mode. You will need to plug it into the modem.

Hi, I have gone trough all steps above but Firefox is still extremely slow.

I have the same setup on both my computers (same add ons, same antivirus and firewalls, same version of windows etc). On the old one firefox works fine but on the new one (which is significantly faster in everything else I do), it is still extremely slow. Both in menues and when writing in textboxes like this one.

I have also checked both in Firefox own task manager and in windows task manager and none of them shows anything strange. I have also again made an attempt to "refresh firefox".

Firefox is my prefered browser, both because of it's privacy and because I'm used to it but currently it is impossible for me to use it because it is so slow that I can not use it when working so I will need to change to Chrome.

Hopefully here will come upp a solution so I will be able to change back to Firefox again. Anyway, thanks for the input.

BR