Friend of the family bought a very nice 32in Samsung full HD set last Nov.

All has worked 100% perfect until yesterday.
All of a sudden the tv displayed a banner "no or weak signal". This appeared on every freeview and freeview HD channel.

So, on looking at this I wondered of the aerial cord had been pulled out by accident.....nope.
I turned on the set top recorder, to see if that was receiving a signal....and it was.....same as normal. I bypassed the recorder by plugging the main aerial cord directly into the tv.....still no signal.
So I did a digital re-scan.......0 channels found. I did this 3 times, still 0 channels.
At this point I asked her if she still had the gurantee...from last November.
I switched off the tv with the tiny rear main switch, and powered it back on, this time going thru the full setup procedure.....still 0 channels found.
As a last ditch attempt, I powered it off and unplugged it for 20secs, then started over using the setup function, and it found all the channels - back to normal.

So, the only thing that worked was a cold restart with setup. I found this quite suprising....I know my Sony is quite old but it never gets turned off at the wall and I have never had to resort to the mains plug (over several year period now).....so is it quite normal in more modern tv's to need a cold restart?

It's fairly normal for any modern computerised item to require rebooting occasionally, and as there's not been a mains switch on TV's for many years, this means unplugging from the mains.

This should always be your first port of call on anything modern.

I would also suggest leaving it longer than 20 secs, 5 minutes or more would be better - sometimes a short unplug doesn't cure it.