After restarting Firefox 4.01 the Flash player no longer appears on any website. On some sites, there's a momentary black box where the player should be. If I click on the YouTube link the same thing happens, but I can hear the audio even though there's no video. I'm running the latest version of Flash and I've followed many of the suggestions on the forum such as activate javascript, disable ad blocking, clear the cache, etc. Flash is working correctly on my other browsers; it's only Firefox that has this problem on only since it crashed overnight.