Paul, I had a "black screen of death" today, the second one since I've had my phone, and both on Fr19.
Here's what happened, hoping it helps :
I managed my contacts on Gmail (website), and when it synced on my phone I turned wifi on.
After it was done, I turned wifi and the screen off in a row.
A short time later, I received an sms. When I pressed the power button, the screen remained black.
But I have Button Backlight Alert installed, and set to have the buttons' backlight brighter on notification,
so I noticed that the phone was still functioning, as the buttons' backlight intensity was changing.
Then I tried and swipe up to unlock the screen, and felt the haptic feedback meaning it worked.
It reminded me of a problem with my previous phone having no backlight when rebooting into recovery,
so I looked at the screen under direct light, as I used to do when experiencing this, and then there was sil... errr... ADW.
I was able to swipe screens, so is BSOD just a backlight issue ?
Not really, because I tried and shut the phone off, and after showing LG logo, it got stuck with buttons' backlight on and nothing more.
Something maybe interesting : I removed/replaced the battery and booted, and wifi was still on...
Another issue : about a week ago, my phone suddenly lost sound and landscape mode... a reboot fixed it.