There is probably a bad capacitor on the power board, I had the same thing happen to my 42LB1DR after 2 years. T.V. would turn on and white power light would blink, no pictue and no sound. If your'e a diy'er, it is not that hard of a fix. Take all the covers off of the back of the tv(UNPLUGGED!!!), then look at all the capacitors on the power board.
These are the capacitors, look to see if any of them appear to have a bump on the top of them. They are supposed to be flat, you can also tell if one of them has gone bad if there is an oily substance on the metal cover that was removed. If one of them is in question, carefully remove the board, and take it to an electronics store to have them sotter ?sp on a new capacitor. It ended up costing me around $40.00 to have this done. Good luck and if you are not comfortable trying this, than take it to a repair shop, but I was quoted around $450 to take the T.V. in. No Thanks