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How can I stop Firefox hanging continuously because of unresponsive scripts?


This has been happening for months, on previous & current installations. I have tried every remedy from Firefox's Troubleshooting pages to no avail. I have tried remedies from other forums (which often give totally opposing advice to that on the Firefox ones!), also to no avail. The issue happens when I am visiting any site that streams videos (BBC iPlayer, 4OD, ITV Player, etc) and in Facebook. It hangs for at least 5 minutes before the "Warning: Unresponsive Script" message appears, & even when I click "stop script" it continues to hang & freezes the whole computer. I have updated all my plugins, tried Firefox both with & without add ons installed. I have tried "Yes Script" as advised by the Firefox Troubleshooter, but with that installed the pages won't load at all. This is driving me nuts, it happens all the time. Using Facebook is nigh on impossible - it takes 20 mins to write a sentence!

Additional System Details

This happened

Every time Firefox opened

This started when...


Installed Plug-ins

  • Adobe PDF Plug-In For Firefox and Netscape 10.1.2
  • Shockwave Flash 11.1 r102
  • NPRuntime Script Plug-in Library for Java(TM) Deploy
  • Next Generation Java Plug-in 1.6.0_30 for Mozilla browsers
  • Windows Presentation Foundation (WPF) plug-in for Mozilla browsers


  • User Agent: Mozilla/5.0 (Windows NT 6.0; rv:9.0.1) Gecko/20100101 Firefox/9.0.1

More Information

  • Top 10 Contributor
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10749 solutions 96724 answers

Helpful Reply

Start Firefox in Troubleshoot Firefox issues using Safe Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

Question owner

Thanks Cor-el,

The one thng I hadn't tried (because the link didn't seem to lead anywhere) was uninstalling the Windows Presentation Foundation plugin.

A combination of this & unchecking the "use hardware acceleration" box seems to have resolved this issue.

For the benefit of anyone else experiencing this, the link for how to get rid of the WPF plugin is here: http://www.ghacks.net/2009/10/18/how-to-uninstall-windows-presentation-foundation-plugin-in-firefox/

Question owner

Right then, I'm back.

I spoke & hit "solved" too soon!

Having spent 24hours with the remedies above applied, I am at a complete loss. It's all gone haywire with the scripts again.

I have now tried every bit of all the related troubleshooters, in various combinations, with no effect whatsoever.

I've even un- & re-installed Firefox, several times.

Anyone got anything further to offer?

Question owner

Hmmm, I've just been updated to Firefox 10.0... maybe that'll help, but I doubt it, as it happened in 7 through 9.

  • Top 10 Contributor
  • Moderator
10749 solutions 96724 answers

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

See "Basic Troubleshooting: Make a new profile":

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

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


Question owner

I've tried that before, as well as doing a complete wipe & reinstall of FF.

I've also done a full system restore & started from scratch, but the same thing happens every time.

I forgot to mention before that the "Unresponsive Script" message also appears every time I try to Clear Recent History.

I just tried YesScript but that didn't help.

I've tried NoScript before, but it wouldn't allow the pages to work at all)