Flash has always been ... risky to run on Linux, because Adobe/Macromedia has historically treated Linux as the red-headed stepchild and, as a result, the Flash plugin for Linux has been unstable at best. Not only did it not work at all, but for much of its history, roughly one in every two to four Flash objects would crash the Flash plugin, which would take Firefox down with it.
I had an opportunity this morning to try out the new plugin sandboxing feature in Firefox 3.6, which runs QuickTime, Flash and RealPlayer plugins in a sandbox environment to protect Firefox in the event that the plugin crashes. I tried, unsuccessfully, to watch a YouTube video preview of Halo: Reach. But instead of Firefox locking up, wedging my CPU at 100%, becoming unresponsive, or dying altogether, all that happened was that instead of a video, I got a lego-block-like icon and an advisory message, "The Flash plugin crashed." Having so informed me, Firefox simply went unconcernedly on with its business as though nothing had happened.
"Sah! The Flash plugin crashed, Sah. No casualties, Sah."
"Very good, Sergeant. Carry on."
"Sah!"