What is causing a black screen appearing while watching freeview programs?

Probably a loss of signal.

The old analog TV could cope with a degraded signal - the picture just got fuzzy.

Digital signal processing requires a much stronger signal to show a picture - as the signal degrades the electronics soon reach a point where they can no longer cope - and they give up - and the screen goes blank.

Perhaps you should look to your aerial system - the cables - and connections.

Peccavi
August 2013