Windows 7 hangs on shut down

Having issues when shutting down Windows 7 on my desktop. Upon shutting down the PC freezes and hangs on the shut down screen. When I force shut down by holding in the power button sometimes it shuts down but restarts automatically by itself. Other times it will shut down but there is still power running through it as the lights on the keyboard (Steelseries MercStealth) and mouse (Razer Death Adder) stay on. There have been no recent software or hardware installs. The only thing that has happened recently is I have connected a powerline adapter to the wall then to the modem via an ethernet cable to send internet to a remote part of the house for the kids. The only thing I can do to shut the whole thing down is to switch it off at the back or at the wall.

Operating System: Windows 7 64-bit
CPU: Intel Core i5 @ 3.30Ghz
RAM: Corsair Vengeance 8.00 dual channel DDR3 @ 665mhz
Motherboard: Gigabyte H77-D3H
Graphics: GeForce GTX 560 tI