Sometimes, when I try to play a YouTube video using Firefox, initially the volume is muted and the video will stop playing within 2 seconds. This often happens when I leave the browser open for a while; things often get fixed, however, when i restart Firefox. What is wrong with the browser, and how can I fix this without having to go through the hassle of closing all of my windows and waiting for them to load all over again? (Also... while the YouTube video doesn't work on Firefox, it will work when I'm using Internet Explorer.)