Peter,
   I found this on a forum page many years ago...maybe it will help?

Derek

Power Options > change Plan settings > Advanced Power Settings

+Sleep
Allow hybrid Sleep > disabled
Allow wake timers > disable/enable try both settings

+USB
USB selective suspend > ENABLE

+When Shareing media [ This is the critical one ]

Set to allow the computer to sleep


On Mon, Jun 25, 2012 at 10:56 AM, Peter Shkabara
<[log in to unmask]> wrote:
> The BIOS is the latest - same as I had in the original board (I had kept
> that one up to date). Alas the system even log shows nothing. It appears
> that the shutdown happens after sleep mode has been activated. This means
> that the CPU is already off and no event can be logged. Very frustrating! I
> don't know how the BIOS code controls the power supply for sleep mode. Could
> it be a bad power supply?
>
> Peter Shkabara
> --------------------------
> [log in to unmask]

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