Upgraded from 10.6.8 to 10.8.2 on xserve - cannot log in

We have two xservers running 10.6.8. In order to run the latest version of Daylite server the OS on the host server needs to be 10.7.4 or higher so we took the plunge and went for an upgrade to 10.8.2.

The download went smoothly, the upgrade kicked off and then the server restarted.

Since the restart the server seems to have changed its name and our admin password does not seem to work now. Is the upgrade meant to reset the accounts on the server? If so what is it likely to have set the password to?