Samsung support got back to me with an email offering the below advice. Keen to try it when I get home... tho I'm not sure that I recall seeing an exit button anywhere. Would this be referring to the power button?
Please follow the below instructions on how to EXIT reset your TV, this should resolve the issues your TV has
1)Press and hold the ?EXIT? button for about 30 seconds up to 1 minute
2)The message ?Resets all settings to the default values? will appear
3)Use the left arrow key to select ?ok? , a yellow box will be around ?ok?
4)Press the enter key (in center of the 4 arrow keys)
5)The TV will turn off
6)Turn the TV back on with the ?power? button
7)Follow ?plug and play? setup
If the issue continues, you will need to download the firmware from our website just click on the link below
and download the ?upgrade file? and FOLLOW the ?upgrade guide?
Purchased the above TV (U40C7000 I think) a few weeks back and everything was great. Was using it this morning no problem. Upon returning home with no changes to my setup, I am met with the 'No signal' error on my HDMI input.
Have spent several hours testing every device connected to the TV on Component, Composite and HDMI. Every input on the TV has been tried and all return a 'No Signal' (however the TV does recognise which input has something plugged in when I press source, as the input plugged in at the time is white rather than gray).
I did get a signal from my xbox via component for about 30 seconds, but promptly lost that and have not been able to replicate.
Pretty sure there's some component in the TV that has died, but want to get a Samsung reps opinion before i sink several more hours into self troubleshooting rather than taking it back to retailer (who will no doubt be out of stock, and I'll be 6 months without a TV knowing m luck).