I had the exact same thing happen to me last night, but mine is model HPT5054x/xaa. Any info on what you did to yours?
My TV (model HPT5054X) is 2 years old and has recently started not to turn on. I hit power and get the sound of the TV turning on but then it just shuts off and then starts trying to turn on and turn off with a recycling clicking noise. When this problem first occured the picture would not come on for a minute or two but the TV at least stayed on and eventually the picture would appear and all would be fine until the next time you try and turn on the TV. The problem became worse with the picture taking longer and longer to appear. Then it just started not staying on but instead going into this recycling mode. I have seen posts that reference the capacitors on the power board but none are bulging and they all look fine. Could they still be bad or is it some other problem such as the power supply? Any help would be appreciated.