What state are the PCs in when you send the command to the Belkin Wemo to supply power? Such as, shutdown/S5, Sleep/S3, or what?
What do you have the Deep Sleep setting in the BIOS, in the same screen as Restore on AC/Power Loss option.
The Restore on AC/Power Loss option option is described as: This allows you to set the power state after an unexpected AC/power loss. That seems like the PC was running, AC power is lost, and this option will reboot the PC when AC power returns, rather than an automatic boot when AC power is applied. So you're able to use this option as a way to remotely start other PCs?