This has happened 3 times now. When I used Autorun for approx 5 mins then "Powersaving Mode" is displayed on my monitor and the PC shuts down !

Any form of timed shutdown has always been disabled on my Windows 7. And I have no hokeys or macros set to 0 (or any other key) that might cause this to happen

i dont think this can be related to origins or arma in any way

You can try and change your autorun button in the menu to something other than 0. I agree with andex though, I am not seeing this as a Origins or Arma issue but something on your machine settings. Possibly your Mobo battery is dying out if it is a hardware issue.

It is a desktop PC, not a mobile

The autorun also doesn't work over most bridges. Nor does it work if you have a broken leg. And it doesn't work for vehicles either (would be useful for boats at least)