I would suggest attempting to reset the television.
First power down the TV and remote all of the connections.
Then, power the TV back on. With the TV powered ON, press and hold the EXIT button on the remote control for 15 seconds. Point it closely to the TV so that it's a constant signal. It should present a "RESET?" option, to which you'd select YES.
See if the reset helps fix this issue.
My brand new UE40C6530 has been working brilliantly for a couple of weeks now - with Wii on component, PS3 on HDMI and Virgin TV on Ext. via scart.
A couple of times the picture has disappeared but come back and now it simply can't find anything. When I refresh it says 'No devices found' although I turned on the PS3, Wii and Virgin too.