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Firefox is already running but is not responding error message

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  • Last reply by cor-el

jmsousa
jmsousa
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Hi. This message "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window." is recurrent. It happened before, I don't remember exactly when, then stopped when a new version was installed. With the last version of Firefox, it returned. I tried all the suggestions available, namely the one in "support.mozilla.org", but with no success. I guess that this is related with something related with the new version, but it is only a guess. I have a laptop running Win 10, with a single installation. This error occurs essentially when I try to open links from Thunderbird (version, 68.9.0), but there are exceptions. A very few links open in Firefox without the error message. Any suggestions how to fix this issue? Thanks in advance.

Hi. This message "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window." is recurrent. It happened before, I don't remember exactly when, then stopped when a new version was installed. With the last version of Firefox, it returned. I tried all the suggestions available, namely the one in "support.mozilla.org", but with no success. I guess that this is related with something related with the new version, but it is only a guess. I have a laptop running Win 10, with a single installation. This error occurs essentially when I try to open links from Thunderbird (version, 68.9.0), but there are exceptions. A very few links open in Firefox without the error message. Any suggestions how to fix this issue? Thanks in advance.

All Replies (2)

FredMcD
FredMcD
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https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/en-US/kb/firefox-takes-long-time-start-up

https://support.mozilla.org/en-US/kb/quick-fixes-if-your-firefox-slows-down


MemTest LAST UPDATED : 27/09/2013
Could you please run a tool from http://memtest.org/
in order to check the integrity of your RAM?

You will need a thumb or disk drive to install it on.


Do you let Windows handle the page file or did you set a fixed size ?

If you use a fixed size for the page file then try the former and let Windows handle the page file.

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

https://www.basezap.com/cant-open-firefox-because-a-copy-of-firefox-is-already-open-mac/

https://apple.stackexchange.com/questions/196771/cant-open-firefox-because-a-copy-of-firefox-is-already-open

http://kb.mozillazine.org/Firefox.exe_always_open

cor-el
cor-el
  • Moderator
  • Top 10 Contributor
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Do you get this message when you try to open a link in Firefox via an external application?

Check the target field in the Firefox desktop shortcut and make sure you do not start Firefox with the -no-remote switch or have set the environment variable MOZ_NO_REMOTE present

  • Control Panel -> System -> Advanced -> Environment variables

If you have a MOZ_NO_REMOTE environment variable then remove this variable and do not change its value to 0 because that doesn't work (Firefox checks for its existence and not the value).