What is connected to the TV for devices (DVD, cable box, etc.), and do you have the same issue regardless of which INPUT you select?
If you press Volume, Input, or any of the other buttons on the TV does anything at all come up on the screen?
What I'm trying to find out is if the screen even shows the Volume, or Input indicators when you press them.
Additionally, is the power light on the front of the TV blinking or flickering?
Please disconnect the set from AC power, then press and hold the power button on the TV itself (not the remote), for 10 seconds. After another minute, plug the set back in and press power once. Do you still have the same problem?
Unfortunately I do not have good news for you. There is no sequence of buttons you can press the reset the TV, and it will require circuit testing and component replacement to operate properly again.
There are basically three problems that would cause this, the Power Supply, the T-Con board, or the LCD panel itself has failed. Voltages need to be measured at the power supply outputs, using a DMM with nothing connected to it but AC Input. If the readings are proper, then the other boards need to be connected one at a time, until one causes the voltage to shut down at the output. Price to replace the power supply is around $200 parts and labor. If the supply outputs power with all of the boards connected, then the T-Con needs to be tested. The T-Con will run you around $150 to have replaced. If the T-Con tests good, then the LCD Panel has failed and will cost you more than a new TV (around $700) to have replaced and it is not cost effective to repair this set. I wish i had better news on this set, but the symptoms you're having indicate a failure in one of the components responsible for powering, and processing the LCD panel itself (including the LCD panel).
If you do not have experience testing live voltages on a circuit board level, then I would suggest using the link below to locate a tech in your area: