"Plugin container for firefox .."

Are you sure that message is from Firefox, and not from Flash?

Maybe post a screenshot of that message for us to see?

https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

It is best to use a compressed image type like PNG or JPG to save the screenshot and make sure that you do not exceed a maximum file size of 1 MB.

Then use the Browse .... button below the Post a Reply text box to upload the screenshot.

I am fairly certain it is the plugin container rather than Flash. I think the screenshot verifies this. This happens when i click Terminate in Flash Builder's debug perspective. If I try to close Firefox with the close button it sometimes hangs and this has caused Flash Builder to crash so I prefer to use the Terminate button. I am constantly debugging so it is getting pretty irritating!

Firefox uses the plugin-container process to run plugin out of the current Firefox process (Out-Of-Process-Plugins) and you may not see the plugin mentioned. Flash uses protected mode by default and that causes two plugin-container processes to be active.

• http://blogs.adobe.com/asset/2012/06/inside-flash-player-protected-mode-for-firefox.html

You can check for problems with current Shockwave Flash plugin versions and try this:

• check for updates for your graphics drive drivers
  https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration
• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)
• disable hardware acceleration in the Flash plugin

See also:

• http://kb.mozillazine.org/Flash#Troubleshooting