Our hln4365 is about 5 years old. It has begun to

What do the flashing lights on the front tell you? The instruction manual lists the troubles indicated by the lamps. If they don't give you any clues, at least try cleaning out the fan and cooling passages to the lamp. Overheating could cause it to shut down... but I think the lamps will tell you. Manual available from Samsung on line, or let me know and I'll dig them out for you. I hope this has helped you.