About 25% of the time when I open Firefox I get the following message in a window..."Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." Why??

I get this message even when I have nothing open. When it happens I restart as instructed and everything is okay for awhile and then it starts again.

Other things that need your attention:
Your above posted system details show outdated plugin(s) with known security and stability risks that you should update.
# Shockwave Flash 10.1 r85
# Java Plug-in 1.6.0_06 for Netscape Navigator (DLL Helper)
Update the [[Managing the Flash plugin|Flash]] plugin to the latest version.
*http://www.adobe.com/software/flash/about/
Update the [[Java]] plugin to the latest version.
*http://www.oracle.com/technetwork/java/javase/downloads/index.html (Java Platform: Download JRE)

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When I try to access Firefox I get this message: "Firefox is already running, but is not responding. To open a new windwo, you must first close the existing Firefox process, or restart your computer."

When I click on Firefox I get a window that says: "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your computer." I can't see where anything is running on firefox. I restarted the comuter and I shut down the computer. I also ran a full scan of the computer.

Sorry I am a PC user but have you seen
* [[Firefox is already running but is not responding]]
Firefox will be hanging for some reason. The quick solutions to kill the process and try again. The next step is to try to see if it will start and exit normally a couple of times, if so the problem is solved. If not the reason needs further investigation.
See [[firefox hangs]]
An immediate likely culprit after repeated problems are the duplicate session restore files, as discussed in the above KB article.

I often get this message. Firefox is already running but is not responding.To open a new window you must first close the excisting Firefox process or restart your system.Thankyou Colin.

So this message appears mainly if I were changing web sites.Can't carry on until I have cleared everything from screen,gone on to my Thunderbird e-mail then Firefox will load again.I can then just carry on till next time.

Please look at [[Firefox is already running but is not responding]]
The initial problem is solved by killing any process firefox.exe, ( & maybe also plugincontainer.exe) Make sure you always close firefox by using the option Firefox Button -> Exit
You may need to investigate further and clear some of the duplicated files that may exist.

When I try to accessFirefox, I get a message that says Firefox is already running ,but is not responding.To open a new window,you must first close the

I get this message when I click the icon on the desktop or open a webpage from O.E.

Make sure that you do not start Firefox with the -no-remote switch appended to the command line.
* http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile
See also:
* http://kb.mozillazine.org/Profile_in_use
* [[Firefox is already running but is not responding]]

I get a message that says ff is already running but is not responding ,to open a new window, you must close the existing ff process or restart your system, how do i close the existing ff process?

I have windows 7 on dell laptop. I am working on a Word Document and want to go to a diff window for some information. I click on the FF icon on my desktop and get a message that says...FF is already running but is not responding. To open a new window, you must close the existing ff process or restart your system..how do you close the existing ff process?
== This happened ==
Every time Firefox opened
== I got my new dell laptop four weeks ago with window 7 installed

See https://support.mozilla.com/en-US/kb/Firefox+is+already+running+but+is+not+responding

When closing FF and then try to go back on, a msg. says FF is already running, but not responding, to open new window you must first close the existing window or restart system. How do i close without restarting?

'This happens after a FF session is ended and am back on my desktop screen. If I then try to go back online a message says that FF is already running but is not responding. To open a new session you must first close the existing process or restart your system. I have to restart the computer to before it allows me to go back on. How can I close the session and then open a new one without rebooting???

Hey GreenViking,
You can kill the process manually by right clicking in the task bar (next to the time and date) and opening the task manager.
[https://support.mozilla.com/en-US/kb/Firefox%20hangs#w_firefox-hangs-when-you-quit-it This article] has some information about Firefox hanging when you try to close it.
Hope that helps!

When I click to open firefox it says that "firefox is already running but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system" and I've tried to shut down and restart my computer but it keeps

when i click to open firefox it says that "firefox is already running but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." and I've tried to shut down and restart my computer but it keeps showing the same message. I've even uninstalled Firefox and then reinstalled in the hopes that the problem would be solved but it this message is still popping up. What can I do to solve this problem?
== This happened ==
Just once or twice
== I was on facebook trying to upload pictures yesterday. ==
== User Agent ==
Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.0.3705; .NET CLR 1.1.4322; Media Center PC 4.0; InfoPath.1)

Do you have a profile lock file in your profile folder? If so, delete it and see if TB runs properly:
http://kb.mozillazine.org/Profile_in_use#Remove_the_profile_lock_file

I close firefox and try to open it again later, it WON'T and says, "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." Firefox isn't running .

After I turn on my laptop and click on firefox it works fine and it opens THE FIRST TIME. So can you help? i DON'T WANT TO RESTaRT my computer everytime and sometimes have to clsoe firefox b/c I'm typing paper and computer goes slow.

Sounds like a "hang at exit" problem. There are several possible causes for that error. See:
* How to stop the running Firefox process
** In Task Manager, does firefox.exe show in the '''Processes''' tab?
** See: http://kb.mozillazine.org/Kill_application
* What may cause Firefox to hang at exit
** http://support.mozilla.com/en-US/kb/Firefox+hangs (see "Hang at exit" section)
** http://kb.mozillazine.org/Firefox_hangs
** https://support.mozilla.com/en-US/kb/Firefox+is+already+running+but+is+not+responding
* You may need to try Firefox Safe Mode
** You may need to use '''Safe Mode''' to locate the problem: http://support.mozilla.com/en-US/kb/Safe+Mode
**Firefox Safe Mode is a diagnostic mode that disables Extensions and some other features of Firefox. If you are using a theme, switch to the DEFAULT theme: Tools > Add-ons > Themes '''before''' starting Safe Mode. When entering Safe Mode, do not check any items on the entry window, just click "Continue in Safe Mode". Test to see if the problem you are experiencing is corrected.
** If the problem does not occur in Safe-mode then disable all of your Extensions and Plug-ins and then try to find which is causing it by enabling '''one at a time''' until the problem reappears. '''You MUST close and restart Firefox after EACH change''' via File > Restart Firefox (on Mac: Firefox > Quit). You can use "Disable all add-ons" on the Safe mode start window.
** See the following for more information
*** http://support.mozilla.com/en-US/kb/Troubleshooting+extensions+and+themes
*** http://support.mozilla.com/en-US/kb/Troubleshooting+plugins
*** http://support.mozilla.com/en-US/kb/Basic+Troubleshooting

Firefox is OPEN and working fine, but when I click a link in Thunderbird I get 'Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.'

If I click a link on my desktop or in any other program (while Firefox is open and running), I get this message: "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." There's about a billion links for this if you Google it, but they all say that Firefox wasn't shut down properly. (OK, maybe not ALL of them, but if the needle is in that haystack, I haven't yet found it.) That's not the issue in my case since I haven't shut FF down at all.
== This happened ==
Every time Firefox opened
== IDK

This began to happen to me when I tried to run two separate profiles simultaneously on the same installation of firefox with -no-remote

Doesn't start when starting as administrator. Error Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

Update firefox, it asked me to update flash, I tried to update flash but it said I had to close firefox. A box came up and said the Flash install would continue when I closed firefox. I closed all firefox windows and no update of flash occurred. I tried relaunching firefox but got the "Doesn't start when starting as administrator. Error Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." message. I rebooted the system, no improvement. I tried to run firefox as administrator and got the same message. Either I find a fix or I won't be able to use firefox and will have to go back to ie.

-> press '''CTRL''' + '''SHIFT''' + '''ESC''' to Open Task Manager -> Processes tab -> right-click '''firefox.exe''' and click '''End Process Tree''' -> close Task Manager
Troubleshooting extensions and themes
* https://support.mozilla.com/en-US/kb/Troubleshooting%20extensions%20and%20themes
Troubleshooting plugins
* https://support.mozilla.com/en-US/kb/Troubleshooting%20plugins
Check and tell if its working.

I deleted the profile and firefox4 and then downloaded firefox4 again. But when i click firefox it says Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process,or restart your system.HELP!

somehow i couldn't get rid of one website called www.searchqu.com/405 set as my homepage... I tried all solutions given to change the homepage but whenever i restarted firefox that homepage used to come automatically.. So, I deleted the profile (even from recycle bin!!) and deleted the firefox and downloaded it again hoping to get my problems fixed (which didn't happen!) because i'm getting dialog box saying- Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

You don't say which operating system you have installed?
Assuming it's Windows, right click a blank part of the Windows Taskbar and go to Task Manager. Then click the ''Processes ''tab, find '''firefox.exe''' and then right click it and choose '''End Process'''.

I try to launch firefox get the following message "firefox is already running, but is not resonding. to open a new window, you must first close the existing firefox process, or restart your system" firefox is not running and restart doesn't work

when I launch firefox get the following message "firefox is already running, but is not resonding. to open a new window, you must first close the existing firefox process, or restart your system" firefox not running and a restart doesn't solve the problem

Download a fresh Firefox copy and save the file to the desktop.
*Firefox 12.0.x: http://www.mozilla.org/en-US/firefox/all.html
Uninstall your current Firefox version, if possible.
*Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.
Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.
*It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
*http://kb.mozillazine.org/Uninstalling_Firefox
Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.
*http://kb.mozillazine.org/Profile_folder_-_Firefox
See also:
*https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding
*http://kb.mozillazine.org/Profile_in_use
*http://kb.mozillazine.org/Recovering_a_missing_profile

Iget this when I try to open a session....Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.task mngr shows no open firefox processes.

I get this when I try to open a session....Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.The task manager shows no open Firefox processes.I had two users on this laptop running Firefox and I tried deleting the program on both users. I then downloaded the newest version, installed it and I still get the error message as before. HELP!!!! I loved the browser program when it was working before and would rather use it than other browsers.

See "Hang at exit":
* http://kb.mozillazine.org/Firefox_hangs
* https://support.mozilla.com/kb/Firefox+hangs

I keep getting this message after closing Firefox and attempt to reopen-Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

I keep getting this message after closing Firefox and attempt to reopen-Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

See:
* http://kb.mozillazine.org/Recovering_a_missing_profile
* http://kb.mozillazine.org/Profile_in_use

When I try to start Firefox I get Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

I get this message when I try to start Firefox after first logging on after turning on the computer.
Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.
Have rebooted. Works when Administrator logs in, just does this in my user profile. Have also re-intalled. Mo change in my User account.
Firefox was working fine for the last 3 1/2 years. Any suggestions?

Firefox is "hanging at exit" when you exit/quit Firefox. 
#Stop the Firefox process:
#*[http://kb.mozillazine.org/Kill_application Mozillazine - Kill application]
#*Windows 7 users click [http://www.techrepublic.com/blog/window-on-windows/reap-the-benefits-of-windows-7s-task-manager/2576 here]
#*Mac users: http://techheavy.com/2011/02/the-mac-task-manager/
#Why Firefox may hang:
#*[http://support.mozilla.com/en-US/kb/Firefox+hangs Firefox hangs] (see Hang at exit)
#*[http://kb.mozillazine.org/Firefox_hangs Firefox hangs (Mozillazine)] (see Hang at exit and Closing Firefox properly)
#*[https://support.mozilla.com/en-US/kb/Firefox+is+already+running+but+is+not+responding Firefox is already running but is not responding]
#Use Firefox Safe Mode to find a problem with an Extension or Plugin:
#*Don't check anything when entering Safe Mode, just continue
#*If the problem does not occur in Safe Mode it is probably and Extension or Plugin causing the problem
#*See:
#**[[Safe Mode]] and [http://kb.mozillazine.org/Safe_Mode Safe Mode (Mozillazine)]
#**[http://support.mozilla.com/en-US/kb/Troubleshooting+extensions+and+themes Troubleshooting extensions and themes]
#**[http://support.mozilla.com/en-US/kb/Troubleshooting+plugins Troubleshooting plugins]
#**[http://support.mozilla.com/en-US/kb/Basic+Troubleshooting Basic Troubleshooting]
'''If this reply solves your problem, please click "Solved It" next to this reply when signed-in to the forum.'''

Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system. How do I fix this? I am ready to go back to internet explorer!

Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.
This box appears and then firefox quits...never opens.
I have uninstalled, and loaded firefox 5 times and never got it to run.

See [[Firefox is already running but is not responding|Firefox is already running but is not responding]].

About 25% of the time when I open Firefox I get the following message in a window..."Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." Why??

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