I can confirm this bug as well. I'm running Ubuntu 8.04 Hardy Heron, it's fully patched and I'm getting crashes very often when I'm watching youtube videos. On the terminal, if I run firefox and this crash happens, an error message appears "Segmentation fault". I'm not sure whether this bug would apply on gutsy with pulseaudio installed. An interesting thing is that I wasn't experiencing such bug until I removed my /home directory and logged in back again.