deleting a machine via NT4 srvmgr is not possible with ldap as backend, probably some becomeroot missing ...:
[2006/08/26 17:08:43.077782, 3] passdb/pdb_ldap.c:ldapsam_delete_sam_account(1687)
ldapsam_delete_sam_account: Deleting user NT4MIG$ from LDAP.
[2006/08/26 17:08:43.077822, 5] lib/smbldap.c:smbldap_search_ext(1179)
smbldap_search_ext: base => [dc=mydom,dc=de], filter => [(&(uid=NT4MIG$)(objectclass=sambaSamAccount))], scope => 
[2006/08/26 17:08:43.077858, 0] lib/smbldap.c:smbldap_open(1009)
smbldap_open: cannot access LDAP when not root..
Are you really using 3.0.21b? If yes, can you please retry with 3.0.23b?
sorry, I use 23b ...
*** This bug has been marked as a duplicate of 4055 ***