Hello, I have 100% same problem as yours. i got it checked at apple and i was offered to replace logic board (no signs of hardware failure) for a huge price. I said no and get laptop back. BUT then i wanted to check if i still have problem: NO, it turned on and worked UNTIL i put to standby!!! I think it has nothing to do with logic board or video chip.
at the moment i am trying to wake it with no success. I'll try to get harddisk out and run it. If it doesn't start even then i'll have no choice.