If you have changed the date /time it will not work.Try that.Probably it is a virus problem,since the PC rebooted by itself.Usually it asks if you want to restart now,or later.I also advise you to check how many ports you have opened,and if any of those ports are open but not used by you at the time,they will bring viruses to your PC and other malware,that can slow down your PC and cause other problems as well.