Vista Computer Awakens Immediately After Entering Sleep Mode

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I spent a few hours last night toiling with Microsoft's software (yet again) - trying to get my new home media center server to better use it's power saving capabilities.

My task was to enable S3+S4 otherwise known as "hybrid" sleep/standby mode working on the system and usable from my Keyspan RF media center remote. This remote has a power button on it that is supposed to allow me to put the machine in and out of sleep mode.

Within Vista I enabled hybrid mode. I also enable S3 sleep mode on the mother BIOS. What I noticed was that if I use the power button on the machine - the machine would enter into sleep mode properly. If I used the remote - the machine would enter into sleep mode and then immediately turn back on. I then verified that the remote receiver was properly enable to "Allow this device to bring the computer out of standby". Still no luck... I then downloaded and configured the cool tool "MCE Standby Tool". Still no luck.

Microsoft KB article KB927821 seemed promising but no luck. Right at the point I was about to give up I found the cause.

What was happening was that during S3 standby the motherboard drops power to USB. Vista is configured to allow this USB device to awaken the machine and therefore interprets the power-down event as such an event and awakens the machine immediately after entering standby. There was a jumper on the motherboard that I flipped to allow the USB ports to be powered during standby. Enabling this resolved the issue and I'm now able to enter and exit standby from my RF remote.