Start>Shutdown>Standby, and goes into Standby. It will not recover from that, goes on holiday forever, stays with black vacant screen, hit any key, space bar, mouse etc, will not bring PC back to life. Only option then is to pull the plug and restart. there must be a better solution. a frustrated Gawk
I had this exact problem click here which as you can see was a result of updating graphics card drivers. The actual update was from 184.108.40.20675 to 220.127.116.1121. After rolling back in Device Manager all was well.
So if you have updated your graphics drivers this could be the cause.