Unresponsive plugin

Warning Unresponsive plugin - What it means and how to fix it

If Firefox shows you a "Warning: Unresponsive plugin" prompt, it means that a plugin, like Flash, is taking longer than expected to do what you requested. This article covers some solutions and workarounds.

Table of Contents

• What action should I take?
• Prevent plugins from hanging
• Disable this warning

What action should I take?

If you get this warning once, you can try to click Continue to give the plugin more time to complete your request. This may not always be successful. If you get this warning a second time you should probably click Stop plugin to make the plugin stop immediately (crash).

Prevent plugins from hanging

Here's what to try if you get this warning often:

• Update your plugins. To check if any of your installed plugins are out of date, visit Mozilla's Plugin Check & Updates page.
• Pause plugins (Flash videos, games, music, etc.) running in other tabs or close those tabs.
  • For more about Flash, see Playing Flash videos makes Firefox hang.

Disable this warning

If you don't want to be warned when a plugin hangs, you can disable this warning by checking the "Don't ask me again" checkbox. When you do that, Firefox will allow the plugin to hang for up to 45 seconds before it crashes.
If you change your mind and want to re-enable the warning, do the following:

1. In the Location bar, type about:config and press Enter.
   
   • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page.
2. In the about:config page, search for the preference dom.ipc.plugins.hangUITimeoutSecs.
3. Right-click on it and choose Reset. 

taken from :
https://support.mozilla.org/en-US/kb/warning-unresponsive-plugin