XFree86 not actioning: Option "DPMS"

[sime <sime@anticd.org>]

Trying to get my laptop to turn off the screen after a certain amount of 
time. In XFree86-4 I have the configuration of enabling DPMS and then 
using one of its features:

Section "Monitor"
        Identifier      "Generic Monitor"
        HorizSync       28-50
        VertRefresh     43-75
        Option          "DPMS"                <<--
        Option "SecondMonitorHorizSync" "28-50"
        Option "SecondMonitorVertRefresh"       "43-75"
EndSection

Section "ServerLayout"
        Identifier      "Default Layout"
        Screen          "Default Screen"
        InputDevice     "Generic Keyboard"
        InputDevice     "Configured Mouse"
        InputDevice     "Generic Mouse"
        Option "OffTime"        "1"            <<--
EndSection

When I log in and run `xset -q` it tells me that DPMS is off. I am 
running Nvidia drivers as well. OffTime will work when sitting on GDM, 
i.e. not logged in.

Running `xset +dpms ; xset dpms 0 0 60` works fine.

-sime