Mozilla has released a quick update for Firefox to increase the time Firefox waits for a plugin to respond before considering it hung up.
For older slower machines, the default 10 seconds is not enough and could cause Firefox to terminate a plugin prematurely, particularly some heavy Flash based games like Zynga’s Farmville, Mafia Wars, and others.
Preference dom.ipc.plugins.timeoutSecs now defaults to more conservative 45 seconds. To set it to a value that better suits your needs, go to about:config and edit it. You can set it to -1 to disable the feature completely.
This is not an urgent update if you are not experimenting false crash detections, so you may want to wait to be prompted. If this affects you, select Check for Updates… in the Help menu.
For more details, check the Firefox 3.6.6 release notes.