Only while watching youtube videos, my dell xps1710 running vista sp2 will immediately poweroff after a few minutes or go to a complete black screen. In actuality the system is still powered with no hard drive activity. An attempt to get it out od hibernation or standby mode does not work and with a complete black screen, the only alternative is to restart by forcing the power off. The issue is that the only time this ever occurs is while watching youtube video. The same system will show movies from dvd all day long.