Sometimes when I start my pc my keyboard doesn't respond

Hi,

Some of the time when I start my pc windows loads but when the desktop opens the pc wont recognise any movement

form my Asus G Series Keyboard and

mouse. The light is on on the mouse so it has power but the num lock / caps lock lights dont come on on the

keyboard This has happened many times now but normally if I hard reboot the pc a few times it is fine. But I'm

just wondering what causes this or how I can fix it. Also pressing num lock sometimes makes it work.

keyboard - Asus G Series Keyboard

mouse - logitech g400

mobo - Asus P8Z68-V Pro/Gen3

cpu - i7 2600k