Can't play Vines, Instagram videos, or gifs on Twitter using Firefox 37.0.1

In the case of Vines and Instagram videos, the audio will play but the video won't. On Twitter, scrolling over gifs/Vines turns them black and/or they do not play. My Flash Player is updated. In about:config, media.windows-media-foundation.enabled is set to true. I've tried setting to false, which just turns off the audio, and switching it back to true, which does nothing. I've reset Firefox. I've re-downloaded it. Nothing seems to be working. Solutions? Edit: Restarting in SafeMode makes it work, so it must be one of the add ons. Edit #2: Figured it out. For those who have the same problem, so to Options -->Advanced --> General and uncheck the Use Hardware Acceleration Where Available box.