42" Planar Plasma turns off

Our T.V. decided to turn itself off by itself last night and refuses to turn back on. When the power button is pushed, either on the set itself or the controller, it turns on but then immediately turns itself back off - no sound, no picture. This is repeated each time I push the "on" button. Any suggestions on what the issue could be or is the thing just a goner. It's about 4 years old by now. Add'l info: it's actually a computer monitor, but unfortunately I don't have the model number. Any help is appreciated! Thank you