The first thing I would check is the power management settings. Under the Control Panel, Power Options, the Advanced tab. There's pull down menu under the heading "When I press the power button on my computer". Set that to Stand by and then hit OK.
The other thing you need to look at is the jumper settings on the P1900. Double check that you have it set right for suspend mode. It's JP1 pins 5-6, and they need to be jumpered for suspend mode.
That should do it.