May or may not help but a couple of things to try,
1. If you haven't, go into the bios and set the "legacy USB support" to enabled from the default auto.
2. Wouldn't happen to have anything plugged into the audio jacks on the keyboard would you? Came across a couple of posts elsewhere that were having a similar problem and that fixed it for them.
This isn't really a Windows problem and more a bios/keyboard problem. You have to remember that when Windows is in sleep mode, it isn't running and neither are the drivers
for the keyboard and it is dependent on the bios recognizing the keyboard to wake Windows.