I have the latest version of Firefox (26.0). I'm not sure if a Flash or Java update caused this issue. Vine videos were playing fine in my browser. This was AFTER I changed the about:config settings for media.windows-media-foundation.enabled to "false" - They never seemed to load when this was set to "true" But now, the problem is back. Vine videos will not play. I recently updated to Firefox 26.0 and this issue came back. Additionally, I did install a Java update. I have tried EVERYTHING to restore my browser to the way it was but nothing works. I have reinstalled Firefox. I have done clean installs of both Flash and Java. I have tried starting Firefox in safe mode, but the problem remains. If I go to a Vine page (https://vine.co/v/heXdnb0m3dm) for example, all I see is a static image. I can't click on anything. It's just a static frozen image. On Twitter, the same Vine video appears as a black screen where it previously used to load just fine. Even on Tweetdeck, which uses Firefox as the default browser, the videos will no longer load. This is all when media.windows-media-foundation.enabled is set to "false" If I change the settings so media.windows-media-foundation.enabled is set back to "true" then the video plays but I have no control over sound. There is, in fact, no sound. The video plays on a loop. No sound. In fact, I can not even control the sound icon. Clicking the icon does nothing. It doesn't change to signify that the sound is on or muted. It remains the same muted icon. So, basically if I try to play Vines by forcing them into flash, I get nothing at all. I get a static image. No video. No sound. No function. If I leave the defaults the same and play them via HTML5, the video plays, but there is no sound and no control. Please help! I have tried everything at this point! UPDATE: I temporarily set security.csp.enable to "false" and the pages load up perfectly. Is this safe, though?