I've seen similar issues with LG sets before. If i had to guess, i'd say it was related to the power supply. LG sets have high power sensing switches in them, that prevent them from turning on if it can't get the power it needs from the supply. If you are not comfortable cracking your TV open, call a local repair shop. If it is indeed the power supply, i'd expect it to cost somewhere around $200 if parts are available.