samba - Feb 2007 - What does mean "lack of trust relationship"?

Ladies and genttlemen, today I realized my Samba server has a problem. I 
had to create some new users and recieved this message after every try:

[2007/02/27 10:56:52, 0] lib/util.c:smb_panic(1599)
   PANIC (pid 31987): pdb_get_methods_reload: failed to get pdb methods 
for backend tdbsam smbpasswd guest

[2007/02/27 10:56:52, 0] lib/util.c:log_stack_trace(1706)
   BACKTRACE: 3 stack frames:
    #0 /usr/sbin/smbd(log_stack_trace+0x2a) [0x8020376a]
    #1 /lib/tls/libc.so.6(__libc_start_main+0xe2) [0xb7ccf852]
    #2 /usr/sbin/smbd [0x8003df81]
[2007/02/27 10:56:52, 0] lib/fault.c:dump_core(173)
   dumping core in /var/log/samba/cores/smbd
[2007/02/27 10:58:06, 0] passdb/pdb_interface.c:make_pdb_method_name(174)
   No builtin nor plugin backend for tdbsam smbpasswd guest found
[2007/02/27 10:58:06, 0] lib/util.c:smb_panic(1599)
   PANIC (pid 32132): pdb_get_methods_reload: failed to get pdb methods 
for backend tdbsam smbpasswd guest

So, I checked smb.conf I adjusted "passdb backend" stanza to tdbsam 
(with no values since the default one is OK to me), but since then some 
users got out of the domain and some machines started complain they can 
not connect to some shared resources because there's no trust 
relationship between them and the server.

To solve the problem with users, I added them again (just a few users) 
to Samba and what is bothering me now is the problem related to 
machines. I've tried add them again to the domain, but no luck with that.

The complete Windows message is: 1789 The trust relationship between 
this workstation and the primary domain failed.

Any hints?

-- 
Miguel Da Silva
Administrador de Red
Centro de Matem?tica - http://www.cmat.edu.uy
Facultad de Ciencias - http://www.fcien.edu.uy
Universidad de la Rep?blica - http://www.rau.edu.uy