That is a hang in the Shockwave Flash plugin. You can check for problems with current Shockwave Flash plugin versions and try this: *check for updates for your graphics drive drivers<br>https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration *disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later) *disable hardware acceleration in the Flash plugin See also: *http://kb.mozillazine.org/Flash#Troubleshooting You can toggle this pref to true on the <b>about:config</b> page to disable protected mode in the Shockwave Flash plugin: *dom.ipc.plugins.flash.disable-protected-mode = true *http://www.ghacks.net/2014/12/21/how-to-disable-flash-player-protected-mode-in-firefox/