See if there are updates for your graphics drivers https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration --------------- https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues

This was not the problem. I am running the current drivers.

Some problems with Flash video playback can be resolved by disabling hardware acceleration in your Flash Player settings. (See [[Flash Plugin - Keep it up to date and troubleshoot problems|this article]] for more information on using the Flash plugin in Firefox). To disable hardware acceleration in Flash Player: #Go to this [http://helpx.adobe.com/flash-player/kb/video-playback-issues.html#main_Solve_video_playback_issues Adobe Flash Player Help page]. #Right-click on the Flash Player logo on that page. #Click on '''Settings''' in the context menu. The Adobe Flash Player Settings screen will open. # Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel. <br/> <br/>[[Image:fpSettings1.PNG]] <br/> # Remove the check mark from '''Enable hardware acceleration'''. # Click '''Close''' to close the Adobe Flash Player Settings Window. # Restart Firefox. This [http://www.adobe.com/support/documentation/en/flashplayer/help/help01.html Flash Player Help - Display Settings page] has more information on Flash Player hardware acceleration, if you're interested. Does this solve the problem? Let us know.

I disabled hardware acceleration but it did not fix the problem.

I think it's time to ask here; Adobe Support https://forums.adobe.com/community/flashplayer