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FF 29 sometimes will not start. Popup with an error message.

  • 68 replies
  • 220 have this problem
  • Last reply by John99

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With FF 29, I frequently get a popup message saying that "Firefox is already running" and I have to kill that process and restart the browser under XP. Is anyone else experiencing this problem?


Hi. With FF 29, I frequently get a popup message saying that "Firefox is already running" and I have to kill that process and restart the browser under XP. Is anyone else experiencing this problem? Thanks.

Chosen solution


Note one potential fix is now in the very recent Firefox Beta 30b8 Initial reports suggest this fixes the issue. (Bug1005487#c38) If you have been suffering from this problem and want a fix now instead of in a few weeks time you may wish to download and install the Beta version of Firefox.

The beta version is effectively a release candidate but is only intended for advanced users or testers. I would be interested to hear feedback from those of you that do test this out.

Beta version download

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All Replies (20)

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I haven't seen anybody report that issue since 29 launched yesterday. How does this happen? Actually what are the steps you do to get this message?

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@Moses and others -

Happens fairly frequently.

Here is the message in a popup box - upon starting FF 29 -


Firefox is already running, but it is not responding. To open a new window you must first close the existing Firefox process or restart your system.

Hope this helps.


Modified by Compumind

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I am finding the same thing in FF 29...especially when opening links from Thunderbird email messages. Both FF and Thunderbird were updated yesterday.

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I had to downgrade to FF 28...which is sad. I liked the new interface but until this bug is worked out I'd rather have a functioning browser rather than a more "beautiful" browser.

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Sorry about the long delay in replying. For some reason, e-mails won't go through about notifications, so I'm going through each thread and replying one-by-one.

It's possible your Firefox program files have become corrupted somehow, you can replace them WITHOUT uninstalling Firefox. You just hide the existing program folder and re-run the installer.

(1) Download a fresh installer from https://www.mozilla.org/firefox/all/ to a convenient location. (Scroll down to your preferred language.)

(2) Exit out of Firefox.

(3) Rename the folder

C:\Program Files (x86)\Mozilla Firefox


C:\Program Files (x86)\OldFirefox

(4) Run the installer you downloaded in #1. It should automatically connect to your existing settings.


Please create a new thread if you need support. /questions/new

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Hi Moses -

Followed your procedure. Result negative.

Can I delete the OldFirefox folder safely?

Compumind :)

P.S. FYI (Still using XP on this box.)

Are others experiencing this problem? Could be something in my system.

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Use "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: Firefox > Quit Firefox; Linux: Firefox/File > Quit) to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar.

You can check the Windows Task Manager for Firefox and plugin-container processes and kill them if necessary.

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Hi cor-el,

Problem only happens when I start FF 29...

Tried this...


No luck.

Anyone at Mozilla devised a patch or new point release to address this? :)

Modified by Compumind

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Problem is now happening after every 2-3 times that FF 29 is closed and restarted. Getting really annoying, sorry to say!

I see that there are others with a similar problem.

Any ideas appreciated. I might go back to FF 28.x, but don't wish to.

How about a quick XP VBS script to kill the firefox process with one click?

Modified by Compumind

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I have tried all the suggested fixes, but none work. Firefox will work first use after booting up (or re-booting) but message reappears on second use. FF 28 works without problem.

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Sorry for posting here...Moses suggested I "start a new question" which I did here: https://support.mozilla.org/en-US/questions/997670

Something is wrong with Firefox 29 and the developers here need to address that. I have reverted back to 28 until they figure out their problem. Luckily, I back up my profile folder weekly. My advise is not to follow all the standard "fix problems" advise the good people on these forums are suggesting...I have been there and done that...it fixes nothing. They are just wrong...something is wrong with FF 29 and I have tried every suggestion, including the terrible "reset" Firefox suggestion, and nothing fixes this. Now someone is telling me to re-install Windows, for heavens sake.

In this thread 32 have reported this problem, in the thread I started 23 have.

A browser should not be a full time occupation just to get it to run right. I am offering as a temporary solution to re-install Firefox 28. This is what I have had to do and all works fine.

Kind Regards,


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@Axis and others,

I tend to agree with you.

I request that someone from Mozilla check into this problem with us. Keep in mind that FF 29 is free and that it is (basically) user supported.

If anyone has this problem, please be sure to post about it, here.

BTW - this problem applies to Windows XP, which I am still using on this box. If the problem is with another version of Windows, i.e. 7, please state that!

Comments appreciated.

TIA :)

Modified by Compumind

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I should add here, to second Compumind's motion, that my wife, who has a account on Etsy selling stuff, told me this morning that there forums were full of people complaining about the terrible experiences they were having with FF 29.

Compumind, I am on Windows 7.

Also, you can't count just the number of people who are posting or marking "I have this problem too." I tried coming in and searching for "FF 29 is not exiting properly" and went through many, many posts before reaching my "new one" and this one. And p.s. FF 29 is also having difficulty creating new bookmarks backups...but that is another issue and as critical as this one.

Good luck all.



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Hi Mozilla,

Can this problem be escalated for all?

Compumind :)

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What troubleshooting steps have you tried? It'll give me a better idea on what steps to perform next

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

See "Creating a profile":

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

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@Moses -

Tried those suggestions and failed.

Tried installing FF 29 on another XP system that never used FF.

Same problem occurred within 10 minutes.

Think the "big guns" should be brought in with a patch.

Ready to go back to FF 28.

Cheers! :)

Modified by Compumind

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I know this must be frustrating. Firefox does not work for you. Firefox is faulty and needs fixing, and you quite naturally presume everyone has this problem.
We do not otherwise the issue probably would have been identified and fixed. As one of the software engineers fixing memory problems says Yeinu

AFAIK Mozilla are nowhere near getting a patch for this. They can not even reproduce this and are unlikely to without our help.

Someone did recently file a bug (1004476) for an issue apparently somewhat similar to this issue.

Unfortunately the person filing that bug however seems to have lost interest in providing full information. One possibility is that the problem in that instance may have been related to clearing cookies & History on closing Firefox. I also noted a comment elsewhere suggesting outdated Norton software may have been implicated previously in some similar issues.

Upthread it was said

I request that someone from Mozilla check into this problem with us. Keep in mind that FF 29 is free and that it is (basically) user supported. 

If anyone has this problem, please be sure to post about it, here.

What Mozilla really needs are two things

  1. Firstly the simplest possible Steps To Reproduce
  2. Secondly trying this in a very basic Firefox configuration
    • A clean install of Firefox (Install Firefox into an empty folder)
    • Using a newly created profile
    • With all plugins disabled
    • Using Firefox Safe Mode
    • It may even be necessary to try using the OS safe mode.

If you do all that you may actually find the problem goes away. If that is the case you are part way to finding the cause. You may even then be in the position of having two configurations or profiles of Firefox one of which crashes and the other does not.

What anyone with this issue needs to remember is that the vast majority of Firefox users just do not see this issue. Software engineers are not going to be able to fix a problem that they are unable to reproduce. If you have the problem, then you can help identify and solve it.

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@john99 -

I have been through the software "rodeo" for my entire IT career and I understand exactly what you are saying. Problem is that I am in a production environment and just don't have the time to devote beyond what has already been posted.

These XP systems will just have to use FF 28 or Chrome for the next 3-4 months until they are retired and replaced with Win 7 machines.

Perhaps the Beta releases off FF have not been tested enough, so you emerge with the dilemma of quantity (releases) vs. quality (solid builds.)

Thanks for chiming in! :)


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Something you could do to get a secure Firefox installed and working, whilst you try to troubleshoot this is to install as an additional browser the third party unofficial build of Firefox Portable ESR. That will even install on a memory stick.

Does that work ?

I also have a couple of questions, the answers to which may assist Moses in helping you to troubleshoot this.

  1. Can you clarify the answer you gave to 'cor-el You said the suggestions in "Firefox is already running but is not responding" error - How to fix did not help. However that is only intended as a workaround. It appears to be what you are already doing. Finding that a Firefox process (or plugincontainer) is already running, and killing it in order to get Firefox to start. So can you confirm that at least is a workaround.
  2. Are you changing any Firefox settings and what security or ad/script etc blocking software is in use on the computer ?
  3. Have you tried in XP s safe mode with networking.

IE Security Fix for IE & XP after EOL
Incidentally assuming you have an official XP and may be using IE note that MS have apparently issued a security fix a couple of days ago and after EOL

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At one time Mozilla started to promote the Beta builds, and experimented with changing channel from the UI. The Beta channel is not now strongly promoted. I wish it was, it may reduce the number of Chemspill point releases that are required.

I also consider it may have been worth holding the many features in Australis in Beta for an extra six week cycle and publicising that for testing instead of throwing it out to Release as normal. The standard beta testing probably does not have enough testers to be efective. I believe the majority of Releases need Chemspill fixes that must cost Mozilla in terms of reputation and development effort.

Have you tried the ESR releases they are probably more suitable for your purposes.

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