Bug#464470: Disabling, and then re-enabling, DPMS does not work.
DPMS works as expected at first, but after disabling and then
re-enabling it, the display will not turn off again. You can trigger
this with an app like MPlayer that disables DPMS on startup and
re-enables it at exit, or simply with xset.
Steps to reproduce:
1) Run "xset dpms 5 5 5". Display turns off after 5 seconds without
input, as expected
2) Run "xset -dpms". Display now stays on, as expected.
3) Run "xset +dpms". Display continues to stay on, even after 5 seconds
To confirm, the relevant xset q output after running xset +dpms is:
DPMS (Energy Star):
Standby: 5 Suspend: 5 Off: 5
DPMS is Enabled
Monitor is On
The only way to get DPMS working again is to re-run the "xset dpms 5 5
5" command, or to re-start your xserver.
I am using the nvidia drivers from stable. According to this bug report
this bug is also present when using the nv drivers.