All apps have disappeared, the only one remaining is in the "favourites" list (BBC iPlayer), but the same iPlayer app does not appear in all apps listing. I've tried rebooting the box, but that didn't help. I've found on this forum that some people had the same problem, but not sure what solution is.
UPDATE: I ran a TV test, and it seem to have identified a problem and said it's going to be sorted out... Had to wait 10 mins, restart the box, and all apps are back. Not sure if this is universal solution, but worked for me... So whatever that was, it's all sorted.