HELP!!! Latest update has killed my ATV

ATV2 yesterday I said yes to the latest update & left it running to do it's thing (we never turn it off).

Have gone to use it tonight & it is 'broken' - no video.

I can get it to play audio & the audio from video via AirPlay but it has no video display at all, nomenu or anything else. Just a blank screen.

It has worked perfectly for years & this has just happened after this update.

I have no idea how to even start with this problem.