[Samba] i can't delete groupmap

[aux]

Hi, i can't delete groupmap in my samba 3.0.12:

# net groupmap list
Domain Users (S-1-5-21-3984604316-2900431957-2958281145-513) -> products
Domain Admins (S-1-5-21-3984604316-2900431957-2958281145-513) -> man
Domain Admins (S-1-5-21-3984604316-2900431957-2958281145-512) -> domadmin
Domain Users (S-1-5-21-3984604316-2900431957-2958281145-513) -> domuser

# net groupmap delete ntgroup="Domain Users"
NT Group Domain Users doesn't exist in mapping DB
Unable to resolve group Domain Users to a SID

# net groupmap delete ntgroup="Domain Users" 
sid=S-1-5-21-3984604316-2900431957-2958281145-513
[2005/07/21 16:14:24, 0] passdb/pdb_ldap.c:ldapsam_delete_entry(276)
   ldapsam_delete_entry: Entry must exist exactly once!

I deleted /var/lib/samba/group_mapping.tdb and restart the server but 
not works.

Anyone help me please?