FireFox and Google chrome vidoes problems

Hi there,
I have a Dell XPS 18 running on windows 8.1, I have been trying to stream videos from you tube using FireFox and Google Chrome and they won't play at all, I have installed the latest version of Flashplayer, when I open the videos using Windows internet explorer, they stream just fine, what could be the problem with Chrome and Firefox? How do I make them Stream videos?
