My PC is no longer waking from sleep by pressing a keyboard button which used to work. I have to restart the PC using the power on button - then I get the a critical error Event 41 - The System has rebooted without cleanly shutting down first. I also get error Event 6008 The previous shutdown at .... was unexpected.

I've run SFC /SCANNOW and that's fine, the keyboard is set to wake the PC, USB selective suspend is disabled, the PC is not allowed to power off USB devices and link state power management is off.

I can't think of any other software changes to try. Is there a diagnostic tool or Fixit program to help solve this problem?

My XFX PSU is playing up taking 10-20secs before the +5VSB signal appears on initial power on. Could this be an issue preventing wake from sleep? Note the PC reboots straight away from a failed wake from sleep as soon I press the power on button - but then it logs the errors Event 41 & Event 6008 noted above.