I'm having the same problem but unplugging did not do the trick for me. I did a hard reset once and it was OK for a day. The problem persisted thereafter.
As of now, the SONY center logo keeps appearing in few seconds loop continuously.
I have had a Samsung UN60KU6300 for about 2 weeks. I hit the home button on the remote to pull up the Smart TV apps to watch YouTube and nothing happens. No menu, nothing. Can't even get to settings, etc. Anyone else having this issue or know why this changed out of the blue?
Bought MU6100 58" and had same problem. Called Samsung and found Power Surge Protector is causing problem.
Per Samsung TV has built-in Power Surge Protector. Now I can use web browser with TV, now.
My UN55KU6270F is 3 weeks old and started doing the same thing yesterday. I also remember a box popping up regarding installing updates...I am assuming this is part of the problem. I had to unplug the TV to get it to work again.