Standby problems

[Porphyro]

I'm at my wits end, and I'm hoping that someone here can lend a hand. I'm not sure which forum this should go in, so I'm putting it here - I apologize if another of the groups would have been more appropriate.
I have a three computer setup. Two Windows XP SP1 boxes both with NForce motherboards. I also am running an EPIA 5000 with Redhat 9.0 installed. The EPIA is serving as a domain controller for both the Windows boxes using SAMBA 2.2.something, and that is working fine (although it took me a while and tons of reading to set it up).
The problem is that once the EPIA was placed into the network, the Windows boxes stopped going into standby. Previously, they would enter STR 3 after a given interval (15 minutes on one box and 30 minutes on the other). Now, they only enter standby when I press the power button. I have gone into the hardware manager on both boxes and disabled Wake on Lan, but that did no good. Now, if I unplug the EPIA from the network and boot one of the XP boxes as a non-domain user, they will go into standby automatically. Just logging in as a non-domain user isn't enough, nor is removing the EPIA from the network after logging in. There has to be a setting somewhere (software or hardware) that corrects this, but I have no idea where else to look. Any suggestions?