[Samba] Problem adding users to the PDC

[Anton K.]

I have problem adding users after I set up a goupmap. Before there was no
problem.
net groupmap ntgroup=Users unixgroup=users
Users (S-1-5-32-545) -> users
useradd pesho -g users
pdbedit -a pesho
new password:
retype new password:
tdb_update_sam: Failing to store a SAM_ACCOUNT for [pesho] without a primary
group RID
Unable to add user! (does it already exist?)
pesho of cource doesn´t exist
pdbedit -L | grep pesho
returns nothing.

I´m using two passwd backends:
  passdb backend = tdbsam:/etc/samba/passdb.tdb \
                   smbpasswd:/etc/samba/smbpasswd
In this case I´m trying to add pesho to tdbsam,
when I remove it and only smbpasswd was in the smb.conf
I was able to add it sucessfully.
I´m using  samba 3.0.7-2.FC1.
Can somebody tell me what have I done wrong?