Leopard/Tiger vs Linux KDC/LDAP

Hi all! I'm having a little problem with my home setup, and was wondering if anyone had an idea what to do. I've got a Linux server set up with OpenLDAP and Kerberos. Basic authentification works fine, but I'm having problems with users that have authAutority set to ;Kerberosv5;;user@REALM.TLD;REALM.TLD. In the ldap structure, KerberosClient is set up and good. My 10.6 SL client machine can authenticate the kerberized users, but not my 10.5 and 10.4 machines. Packet sniffing shows absolutely no differences between 10.4, 10.5 and 10.6. [i]kinit user[/i] asks for password, the ticket is granted. I can't seam to find what, except the OS version, is different between my 3 Macs that makes it work on 10.6 and not others. Anybody can help me with that?