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Firefox 20/21 not responding, even after re-install.



I know this looks like the same old same old, but I have tried all of the existing support queries or occurrences of this that I could find, but to no avail.

So my FF 21 on Win7 suddenly stopped working. Whenever I tried running it, the process would appear in task manager, but no window would appear. No crash report, nothing. This also happened a month ago but the problem 'went away' which was a little disconcerting.

So this time, I have tried uninstalling & re-installing multiple times, including removing all personal data (Backed up elsewhere) each time.

Sometimes when I come to run a freshly installed instance, it will work. Whenever I tried importing my old profile, it would hang before displaying any window.

So I figured I had a bad profile. I have since tried a fresh install followed by running the profile manager. If I click on 'create new' in profile manager, I can create a new profile but it goes to the 'Not responding' state before I can launch FireFox. This is without having any of my old profiles in place.

Currently, I have another fresh install and am not even able to start it with the fresh default profile that was created. Even if I try to start in safe mode, I get the box asking if I want to start in safe mode and upon clicking 'Start in safe mode' the window just goes to 'Not responding'.

I'm at a bit of a loss here as fresh installs now are even leaving me with a hanging FF and not even a clue as to what to look for.

I understand that it may be an issue elsewhere on my system, but without even being able to launch FF, I am unable to diagnose further.



Additional System Details


  • User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36

More Information

smo 45 solutions 498 answers


Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

  • You can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
  • Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

Thank you.

Question owner

Unfortunately, as I said in the original question, it does the same in safe mode...

"Even if I try to start in safe mode, I get the box asking if I want to start in safe mode and upon clicking 'Start in safe mode' the window just goes to 'Not responding'."