monitor goes into energy saving mode suddenly machine locks up

[automaton]

all of a sudden my machine and monitor goes into energy saving mode and wont come out
then I cant turn it off by 5 second power button or reset only by d/c the power supply
HELP

[watercooled]

Does it happen randomly or is it just failing to resume from standby/sleep?

[K3V]

if you're unable to power down by holding the power button in - it would usually suggest some failing hardware

but as above, when does the problem occur