For several months I've used the the Wake on LAN feature (from Windows shutdown) with my Motherboard GA-H77M-D3H from Gigabyte with an internal "Qualcomm Atheros AR8151 PCI-E Gigabit' NIC under Windows 8 x64. Suddenly, and this was really suddenly, because it worked for months and I didn't change any BIOS settings, drivers nor energy policies in Windows in the past - it just stopped working. The computer couldn't be enabled with the usual Android app 'Wol Wake on Lan Wan' I've used for this nor through my router (both with the use of so called magic packets). Also it couldn't be a change I've made myself on my OS because there were none made.
I've investigated the problem and saw that after Windows shutdown (Windows sleep or hibernate weren't affected) the NIC of the motherboard was powered off. This was indicated by the led lights on the RJ45 port on the backside of my computer and also the leds of the respective port on my router - they went off like there was no cable connected, or just no power.
I've tried several approaches to find a solution. I've tried reloading of the "optimized values" in BIOS setup, BIOS updates, disabling/reenabling the "Allow this device to wake the computer" in Windows device manager. They all didn't work.
Then I just installed the NIC driver from the Gigabyte website and after a restart it worked like a charm.
I don't understand this, my computer worked months with the native driver of Windows... From the beginning of the Windows installation I didn't install any drivers from my motherboard manufacturer because Windows 8 supported all of my hardware by native. Also I couldn't just buy a PCI/PCIe network card to have another 'test subject' because then I would block the ventilation of my graphic card.
This is one of the problems with computers you can spend hours on to find a solution and you even don't know if this was the right correlation between cause and effect. Also you normally don't understand the WHY. I don't like this.