I was getting the same error on a Linux server, after a not so graceful shutdown of ArcGIS Server, I ended up finding a processes " C:\windows\system32\explorer.exe /desktop" which looked odd to me, i kill it, and restarted ArcGIS Server and everything came back up. The " C:\windows\system32\explorer.exe /desktop" process came back up too, this is clearly launched by ArcGIS Server.
hope this helps someone in the future.
-Andy