[Samba] i hav a problem

[SysAdmin]

	i'm trying to use a linux PDC with samba... so i took the docs and 
read them... and i've edited the smb.conf file and then tryed to see if it 
worked... the machine logged into the domain and asked for restart ( the 
test machine runs windows XP Professinal)... after the restart i tryed to 
logon to the domain... it doesn't work... so i started a network packet 
logger to see what's wrong (the message box didn't say anything 
relevant)... the error code was something like permision denied ( 
NT_PROTOCOL_UNAVAILABLE or somethin like that)... the rpcclient also 
returns the same answer... the password server works... if i try to logon 
to a share using a domain registered username it works... but if i try to 
logon with that user it doesn't work... the maschine is running RH Linux 
8.0 kernel 2.4.20-2.48 samba server 2.2.7a... what can i do?