[Samba] Domain join problem

[Gary du Bois]

Hi I am having a problem joining a domain, please assist

here is my smb.conf file:
[global]
        workgroup = CORP
        realm = CORP.GO2UTI.COM
        preferred master = no
        server string = Samba Server
        security = ADS
        username map = /etc/samba/smbusers
        log file = /var/samba/log/log.%m
        max log size = 50
        dns proxy = No
        password server = 10.8.240.65

[samba_test]
        comment = samba_test
        path = /provar
        valid users = @dev
        read list = @dev
        write list = @dev
        create mask = 0766

Kerberos settings are valid and I can do a kinit and klist

When joining the domain:

$ net ads join -S JNBMPP03 -U sambajoin
Enter sambajoin's password:
Failed to join domain: failed to set machine spn: Constraint violation

Now if I change the hostname to V240rd1:

$ net ads join -S JNBMPP03 -U sambajoin
Enter sambajoin's password:
Using short domain name -- CORP
Joined 'V240RD1' to realm 'corp.go2uti.com'
No DNS domain configured for v240rd1. Unable to perform DNS Update.
DNS update failed!

This join works, obviously the shares do not work as there is a
different netbios name

Now if I change the hostname of the system to V240rd1 by editing the
/etc/nodename, and then reboot the system

Retrying the join:
$ net ads join -S JNBMPP03 -U sambajoin
Enter sambajoin's password:
Failed to join domain: failed to set machine spn: Constraint violation

Change the hostname to V240-rd-1

$ net ads join -S JNBMPP03 -U sambajoin
Enter sambajoin's password:
Using short domain name -- CORP
Joined 'V240RD1' to realm 'corp.go2uti.com'
No DNS domain configured for v240rd1. Unable to perform DNS Update.
DNS update failed!

???? Can someone explain this?