Firefox 3.6.6 has been released to fix the issues that most people were experiencing with the plugin-container or crash protection feature introduced in the 3.6.4 release recently as mentioned here. This latest release modifies the crash protection feature to increase the amount of time that plugins are allowed to be non-responsive before being terminated (Bug 574905).
What is plugin-container
In Firefox 3.6.4 and above, some plugins are loaded separately from Firefox in `plugin-container.exe`, allowing the main Firefox process (firefox.exe) to stay open even if a plugin crashes.
Which plugins are supported by plugin-container.exe?
For more information about plugins, see Using plugins with Firefox.
Update: A new version has been released which fixes several critical bugs that were present in version 3.6.6. All users are advised to update their browser to the latest version. Click here to read more about the update