I've been searching a lot about this. On my PC (latest version of Flash and Firefox as of 9/2014) my Firefox becomes unusable when Flash runs. The general procedure to fix this issue is to load a Flash test page, right click on it, go to Settings, and then uncheck Hardware Acceleration. (As explained in this link: https://support.mozilla.org/en-US/kb/keep-flash-up-to-date-and-troubleshoot-problems#w_playing-flash-videos-makes-firefox-hang) I am completely unable to even right click on a Flash object. It freezes. I have read another article about disabling mic/speakers, and that doesn't work. I'm hoping there are registry/mozilla settings I can change that mimic the "right click.. uncheck Hardware Acceleration."