I have a problem kind of like that.
I can't change the screensaver or power settings, the monitor
always shuts down after 15 minutes of inactivity.
I have even tried to change it in safe mode and admin mode
without favorable results.
I wish there were a way to disable ACPI control so that
it has an always on setting that's always on.
I almost forgot to mention that in order to turn off my computer
I have to select restart then hold in the power button at POST
Perhaps these problems may be related, something I may have overlooked or can't
change, like the hibernation and or sleep settings.