I experienced the same problem. Top LCD on but camera was in reality off, nothing worked. I then noticed that the top LCD was indicating that the second memory card was highlighted although I was positive card #1 was empty. Could not access card one in the camera. Put card #1 in my card reader and formatted it in the computer then put it in the camera and it did recognize the card. Reformatted in the camera and no problems since. One shot problem. I'm assuming the card somehow became corrupted but the formatting in the computer somehow solved the problem.
Tom From Beautiful Smith Mountain Lake in Virginia