Hi Chris, ok this is what I have just done as my laptops currently have no antivirus on them at all.
I reinstalled an offline version of Avast, version 2280 which I downloaded in October 2016.
I then updated all the virus definitions.
Everything worked 100%, so I updated to the latest 2294, bingo there goes my webcam, displays a blackscreen.
So I set Avast to passive mode, it asks for a reboot, which I do, once rebooted after a minute or 2 Avast pops up suggesting I disable Passive mode, which I do, then says “we’re getting ready to actively protect your computer”, then it says “You’re Protected” and that’s that all works 100%.
The laptops run 24/7 so no problem there about shutting down 
Thanks for the link Asyn, hope something happens tomorrow, will report in.