monitor will not standby
 

I'm running Slackware 10.0, GNOME, with a Mitsubishi DiamondPoint M55 LCD and it will not go to standby. I've switched over from winXP pro, and on winbloze I had it set to go on standby after 20mins. I worked, after 20mins the green light on the monitor went yellow and it went on standby, then awoke by moving the mouse. On Slackware it will not standby. I have the "display power management set to "standby after 10min", "suspend after 20min", and "off after 30min". The screensaver pops on after 5mins then standby comes on after 10min but the monitor doesn't go on standby, instead the light stays green and the screen goes blank but is backlit. Am I missing something? Is there a option i'm not seeing? Do I need some kind of package to be able to do this? Is this normal? How can I get my monitor to go on standby?

Try for "suspend" or "power off" instead of "standby". They all apply to the monitor.
Set "standby" to one minute,
"suspend" to two, and
"power off" to three, and just watch for the right one.