I always carry a charger with me, a girl here at work however forgot it one day when I was supposed to be installing Ubuntu Netbook edition on her 9 which died midway. It did start right back up again upon charging but ended up needed to be installed again.
So the moral of the story is two fold, have a second charger, and never install an OS or run updates with out being plugged in.
Yeah though, if it's still under warranty I'd call Dell before it's up.
Now granted, I have three Dell netbooks, so I have a charger at work, one at home, and one I carry in my bag.