DPMS not turning off LCD screen

[Stephen J. Roznowski]

I have a Sony SDM-HX93 LCD monitor running off an Nvidia GeForce FX
5500.

I have the DPMS option set in my xorg configuration file, but while
the screen turns off, the monitor never enters power off mode (it
remains 'backlit').

Any suggestions where to look for the error?

Thanks,
-- 
Stephen J. Roznowski    (sjr at comcast.net)