I have been having the black screen problem with sound also, turning the TV on and off gets my picture back for so long, after reading this I tried changing the display but it always showed on current when I went back into it. What I have done is turn all the settings off, ie back-light and a few other things that were turned on, there was also another brightness setting at 100% i put that to 50, any setting that is on turn off, obviously without making your picture bad and my TV has been fine for about 30 minutes, it was going black every 5 minutes before I did this.