This error means that a plugin (like Adobe Flash) has crashed. Simply reloading the page will restart the plugin, and your video (or other content) will be shown again. Before reloading the page you can add a comment to explain how it happened and send a crash report to Mozilla by clicking on Send crash report. These crash reports help us make improvements to Firefox.
A plugin is a piece of software that displays internet content that Firefox is not designed to display. This usually includes video, audio, online games and presentations that are made in patented formats. Plugins are created and distributed by the companies that make those patented formats. Some common plugins are Adobe Flash and Microsoft Silverlight.
A crash happens when a piece of software abruptly stops working. Plugins sometimes crash for various reasons, and cause Firefox to crash along with it. For more information about Firefox crashes, see Firefox crashes - Troubleshoot, prevent and get help fixing crashes. Some plugins load separately from Firefox, allowing Firefox to stay open if the plugin crashes.
Crash reports only include technical information to help Firefox developers determine what went wrong, and how to fix it. These reports do not include personal information. The information sent in a report includes:
Many problems with plugins can be solved by updating to the latest version of the plugin. To check if any of your installed plugins are out of date, visit Mozilla's Plugin Check & Updates page. The name of the plugin that crashed can be found in the error message.
Breakpoints can trigger Firefox's hang protection. You can disable hang protection by setting the dom.ipc.plugins.timeoutSecs preference to -1. See the Mozilla Developer Network documentation for details.