Our Samsung TV (LE40C750) suddenly stopped recognising the inputs on the HDMI ports. It recognised them being plugged in and unplugged but had no signal.
After scouring the web and coming across horror stories about having to replace the motherboard I came across one post that suggested powering off all the devices connected to the TV, waiting and then powering everything on again.
Remarkably this worked! So thank you to whoever it was who worked it out; you probably saved me a lot of money.