This is some standard guidance that addresses the most common issues with the Flash Player plugin. I'm sure you've seen some of it before, but just in case: (1) If you have any recorders/downloaders that interact with Flash media make sure they are as up-to-date as possible, or disable them temporarily. (2) Disable hardware graphics acceleration in Firefox and in Flash (A) In Firefox, un-check the box here and exit/restart: "3-bar" menu button (or Tools menu) > Options > Advanced > General > "Use hardware acceleration when available" (B) In Flash, see this support article from Adobe: http://helpx.adobe.com/flash-player/kb/video-playback-issues.html#main_Solve_video_playback_issues (3) Disable the protected mode feature. It has security benefits, but is not compatible with all systems for some reason. You can do that by creating or editing a settings file. The following pages/posts provide different approaches: * Adobe support article under the heading "Last Resort": [http://forums.adobe.com/message/4468493#TemporaryWorkaround Adobe Forums: How do I troubleshoot Flash Player's protected mode for Firefox?] * Manual steps: https://support.mozilla.org/questions/968190?page=5#answer-509209 * Batch file to automate the manual steps: https://support.mozilla.org/questions/982093#answer-518078 Flash needs to completely unload from memory (exiting and starting Firefox up again might help) before this takes effect. Any improvement?