The hard disk does go off after 20 minutes, the display goes off after 2 hours and the screensaver activates after 15 minutes and displays the logon screen on resume.
The processes to speak of could stop DS from cycling (they are more destructive than you think). Also, Windows does not always do an elegant job of recovering from them or in the order best suited for DS to continue as it was (other apps as well for that matter).
As a test, I would wean down each to see what may indeed be more destructive than any other.
You can also wait for Windows to fully come back and try to manually restart Windows Explorer. You can create a batch file to run after:
taskkill /f /im explorer.exe
ECHO Waiting 5 seconds to restart WinExp...
Timeout /t 5 /nobreak
Save that as WinExpRestart.bat on your desktop and try.