[Samba] HELP!

[Marco Musico']

Hello folks!

I've got stuck in a problem after setting up a Linux box as a PDC for a 
Windows network with Samba.
The stuff was running pretty well up until we tried to setup and install a 
printer on the Linux box; I saved the old configuration (smb.conf file) and 
then I started to change some lines in it to allow printer sharing... my 
nightmare started to be real since then!! Now no user on any pc can log into 
the domain; root can add machines in the domain (and the machine account is 
created too..) but cannot log in.
Apparently the server behaves as a "stand alone" one even when "testparm" 
shows it's a PDC; infact I can log into any Windows machine with a local 
user and I am able to browse the server by running "\\server": Samba asks me 
for user/password and the let me in; at that point I can brose the shares, 
open files, save files and so on.

Now my question is: what have I done wrong? It's clearly something we 
changed in smb.conf or so that is making us having an headache.

I am including smb.conf, log.smbd (with a level 5 debugging).

Any help will be really appreciated!

Best regards

Marco Musico'