We had an instance where everyone's username was their SID for awhile, a long string of characters, instead of using the sAMAccountName. By default it has always used the sAMAccountName without any special configuration.
Where is this configured and what would cause it to use the SID instead?
The system that had the problem is setup use the standard Kerberos connection, not LDAP (I know there is a specification of which metadata to use for username in the LDAP server configuration).