PAM authenication

ok - fairly new to postgresql & tring to set up tcp/ip access using pam
authentication
using gentoo_linux 1.4_rc2
postgresql-7.3.1


my pg_hba.conf file has the entries

# TYPE  DATABASE    USER        IP-ADDRESS        IP-MASK           METHOD

local   all         all                                             trust
host    all         all         127.0.0.1         255.255.255.255   trust
host    all         all         192.168.1.1       255.255.255.0     pam
postgresql


my /etc/pam.d/postgresql file has the entries

#%PAM-1.0

auth       required     pam_stack.so service=system-auth
account    required     pam_stack.so service=system-auth


when i try to connect (locally)....
 # psql test -U brett
Password: (password entered - i know it is correct)
psql: FATAL:  PAM authentication failed for user "brett"


i get the following entries in /var/log/auth.log - and a
Jan 31 16:31:47 achilles unix_chkpwd[25987]: check pass; user unknown
Jan 31 16:31:47 achilles postgresql(pam_unix)[25986]: authentication
failure; logname= uid=70 euid=70 tty= ruser= rhost=  user=brett

'brett' has a system level account.
i can connect as user 'brett' if pg_hba.conf is set to 'trust', but never
when pam is involved...

any ideas? i've been mucking around with this for a couple of days & not
getting very far

regards,

brett