Aktualizuj BIOS, povypínej wake up events, mělo by to jít vyřešit nastavením power managementu BIOSu.

Btw tohle máš napsaný v manuálu:
Questions 2: Why is the light of my keyboard/optical mouse still on after computer shuts down?
Answer: In some boards, a small amount of electricity is kept on standby after computer shuts down and that's why the light is still on.
Pak to ber jako vlastnost své desky...