Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

Suggested solutions do not work for "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

  • 4 replies
  • 13 have this problem
  • 6 views
  • Last reply by rambosauce

rambosauce
rambosauce
more options

I keep getting the error "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

I attempted all recommended steps I could find on support (task manager, profile permission settings, etc.) and none of which worked. I even uninstalled Firefox and used other browsers for over a month. Upon reinstallation and launch I keep getting the same error. At this point I've exhausted all the advice I could find on this forum and hope I do not have to abandon Mozilla.

I keep getting the error "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window." I attempted all recommended steps I could find on support (task manager, profile permission settings, etc.) and none of which worked. I even uninstalled Firefox and used other browsers for over a month. Upon reinstallation and launch I keep getting the same error. At this point I've exhausted all the advice I could find on this forum and hope I do not have to abandon Mozilla.

Chosen solution

Thank you both for the reply, I understand things are busy.

I am on Windows 7 and had previously tried reinstalling the newest version of Firefox.

I went a little aggressive and deleted the entire Mozilla folder in the AppData directory. Now the newest version has installed and launched with no problem :)

Reinstalling plugins is trivial to go back to using my favorite browser. Cheers!

Read this answer in context 👍 0

All Replies (4)

rambosauce
rambosauce Question owner
more options

Guess it's goodbye Firefox! It was good while you worked!

FredMcD
FredMcD
more options

Sorry you never got a reply. Sometimes, we get so many requests for help, that some get lost.

What is your computer system and Firefox?

Have you updated to the current version?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. Is the problem still there?

cor-el
cor-el
  • Moderator
  • Top 10 Contributor
more options

Did you try to delete the parent.lock file in the Firefox profile folder?

  • C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

"AppData" (XP: Application Data; Mac: ~/Library; Linux: ~/.mozilla) is a hidden folder.

rambosauce
rambosauce Question owner
more options

Chosen Solution

Thank you both for the reply, I understand things are busy.

I am on Windows 7 and had previously tried reinstalling the newest version of Firefox.

I went a little aggressive and deleted the entire Mozilla folder in the AppData directory. Now the newest version has installed and launched with no problem :)

Reinstalling plugins is trivial to go back to using my favorite browser. Cheers!