Your log contains an IP maybe remove this if your problem is fixed, not much anyone can do with it although it's better to be safe then sorry right?
A couple things you should try...
Re-download your server software.
Check the date/time on your server.
Make sure you allow the server through your firewall. (if your on windows when you first started it should have prompted you)
Check downdetector.com and make sure the the authentication servers are not down.
I could list a thousand things but many people get this error and a lot of people blame Microsoft but it could be anything from the NTP servers to a miss-configured file.