[MDDI]

Have you checked the NIC in Device Manager? Right click the NIC / Properties / Power Management Tab. Uncheck "allow computer to turn off device".
It appears that Realtek is using one driver for both desktop and laptop. Definately use the driver from Realtek or Gigabyte site, not Windows update.
Not real sure when the Power Management feature was included with the Realtek drivers, but I think it's recent.
I just replaced my X48T board and had not updated the NIC driver for awhile, I'm fairly sure the Power Management feature was not there and I don't remember what the driver revision was.
The driver disk that came with my EP45T (same NIC as the X48T) definately had the Power Management feature icluded with the Realtek driver, I found it when I started loosing my internet connection, so I don't know what driver revision that feature was introduced.