Try unpluging it for 2 to 3 days then plug it back in and push the power button and it should come on, if not, then you will have to get it repaired and it will probably cost about 1/2 of what the tv is worth and it will eventually develop the same problem again a few years down the road, so if unpluging it didn't work it might be better to just buy a new tv, just don't get the same brand. Oh and whatever you do, never turn the tv off or you will have to repeat the same process of unpluging it again.
Precious
June 2009