Kerberos Event 4 servername showing username

Solution 1:

Glad you solved your own problem, but it doesn't sound like you understand why what you ran solved the problem.

Bottom line, the SPN needs to be set on the appropriate object. It sounds like you had the SPN set on the computer's object in AD that was running the service. That's why things started working if you changed the service to run as SYSTEM. But if you change it to run as a domain user, you need to move the SPN to that user. And it's important that you move it (read: delete it from the computer account) and not just copy it. Duplicate SPNs will break things.

Solution 2:

Found the solution here: http://blogs.technet.com/b/dcaro/archive/2013/07/04/fixing-the-security-kerberos-4-error.aspx

I ran:

setspn -A HTTP/$servername$.$domain$.com.au $username$

and that fixed the problem