Exact same symptoms for me : on boot up, green light would stay on for 1 second, then shut down. Without wifi, green light would stay on, but blank screens. In fact, it's because on boot up, DS will check if wifi is present, and stop if there is an error. Then, it checks for upper screen, and after that, for lower screen. If one of these is not responding, DS will turn off. I check my cables (upper screen) and DS started again with no problem.