It's possible, but I'd expect to see "Error 7400: Unregistered box" or similar wording, in that case.
In logical order, on the box with EPG problems: Assuming the physical connections are tight and clean, does live TV (pick a channel beyond the terrestrial 5) work ok - this proves the incoming feed. Does a CatchUp program work ok? This proves the return path & VOD connections ok.
Assuming all good so far, follow Home > Help & Settings > Settings > Network, and check when the last good connection was, or what the reason for failure is. You can also try a fresh connection from here.
Try these and we should have a much better idea where your problem lies.
There are several "To Be Announced" below the terrestrial channels. Tried a connect to virgin services which failed.
I was just visiting and couldn't investigate any further. Hopefully on the basis of him being aged 87 and a techniphobe he should hopefully get an engineer call out and not get put through the call centre mill.
Weird that I had the similar issue some weeks ago.
Not one I can deal with now, but thanks again for response.