Blanked screen never returns

[MR ZenWiz]

Since I upgraded my home desktop to Xubuntu 16.04, and installed 16.40
on my laptop, I have noticed that when the screen is blanked (or
powered down), it never comes back.  Rebooting resolves this (the
windows solution - ugh).

My desktop is a custom built i7 16GB system with a 28" iInc 1980x1200
DVI monitor, and the laptop is an HP 8710w that also happens to have
1980x1200 res on its native screen.  (Is there any connection?)

On the desktop, xscreensaver never blanks the screen anymore (it did
without incident in 14.04), but when I power off the monitor
externally, upon power up the screen remains black and the computer
never seems to see it.

On the laptop, I have it set to "do nothing" when the laptop is closed
(power stays on, machine still runs, but the screen is automatically
shut off when it's closed), but again it never comes back.  Well,
almost never - the night before last I had closed it when I went out
and when I came back, it wanted to be rebooted, so it came back to
life.  after reboot, the same problem occurred - consistently.

Is this the same as this problem
https://bugs.launchpad.net/ubuntu/+source/xfce4-settings/+bug/1575123?
 I have no TV set involved, only the desktop DVI monitor and the
laptop's native screen.

I'm not certain if I have the "Configure new displays on connection"
set on my desktop (never needed it), but I'm pretty sure it's on on
the laptop (I know it was before I had to install 16.04 because the
upgrade from 14.04 failed).  I'll have to check those when I get back
to them.

On the assumption that this is not the same problem, is there another
solution?  I don't recall if I ever had to set one of the APIC or APCI
options in the boot line - on the desktop I did before I gave up on
AMD CPUs a year or two ago, but not since using an i7.

Thanks.
MR