This just happened to me not even a few minutes ago. I had just put my 3DS in my coat pocket after playing a game, walked down a hill to my room, took it out, and found that not only had it shut itself off, but it will not turn back on. I do not think it is a battery problem, as I have it plugged into a charger right now, and it still won't work. The battery wasn't even running low when I put it in my pocket.
Is there anything I can do to get it to work again? It's sitting on the charger right now, and the charging light is even on, so something's still gotta be working in it. I should also mention it suffered a direct impact from someone walking right into my extended hand, but it was working fine after that.
Words cannot express how much I'm hoping it's not busted. I have the absolute worst luck with handheld systems ever since the first DS came out. :(