@HamzaDjebli: I have Firefox 22.0 and just tested this video: http://channel9.msdn.com/Events/Imagine-Cup/World-Finals-2013/Day-0-Imagine-Cup-Finals and the controls on the Silverlight player worked for me. I tried pausing/playing/scrubbing/adjusting the volume. Can you give me a specific video to try or is it happening for you on every video? What happens exactly and what version of Firefox are you using?