I installed Samba 3.4.6 binaries on RHEL 5.0. 

smb.conf:

# Samba config file created using SWAT
# from UNKNOWN (127.0.0.1)
# Date: 2010/03/06 16:31:09

[global]
        workgroup = EXAMPLEDM
        realm = EXAMPLEDM.COM
        netbios name = EXAMPLE-34
        server string = Samba Server Version %v
        security = ADS
        password server = example-86.exampledm.com
        username map = /etc/samba/smbusers
        log level = 3
        socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
        local master = No
        domain master = No
        dns proxy = No
        wins server = example-86.exampledm.com
        idmap uid = 10000-20000
        idmap gid = 10000-20000
        template shell = /bin/bash
        winbind enum users = Yes
        winbind enum groups = Yes
        winbind use default domain = Yes
        cups options = raw

[homes]
        comment = Home Directories
        read only = No
        browseable = No
        browsable = No

[printers]
        comment = All Printers
        path = /var/spool/samba
        printable = Yes
        browseable = No
        browsable = No

[test]
        path = /test
        write list = +Administrator
        read only = No
        guest ok = Yes

/etc/pam.d/samba:

#%PAM-1.0
auth        sufficient    pam_winbind.so
account        sufficient    pam_winbind.so
password        sufficient    pam_winbind.so
auth    required  pam_stack.so service=system-auth
account required  pam_stack.so service=system-auth

The server REDHAT-34 was joined to the Active Directory domain EXAMPLEDM. The commands kinit, net ads user, etc. worked fine.

However, I cannot start winbindd from the script /etc/rc.d/init.d/winbind. The error messages in the log were:

[2010/03/06 10:24:18,  0] lib/util_sock.c:1790(create_pipe_sock)
  bind failed on pipe socket /tmp/.winbindd/pipe: Permission denied
[2010/03/06 10:24:18,  0] winbindd/winbindd.c:1406(main)
  winbindd_setup_listeners() failed

When I ran "/usr/sbin/winbindd" directly, the winbindd processes were started. However, I was not able to connect to the samba server as an AD user:

[root@example-34 samba]# smbclient -L example-34 -U awang
Enter awang's password:
session setup failed: NT_STATUS_LOGON_FAILURE

I did strace on the smbd processes and found the following in the strace output:

lstat64("/tmp/.winbindd", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat64("/tmp/.winbindd/pipe", 0xbf9c30ec) = -1 EACCES (Permission denied)

What went wrong? Any help would be very much appreciated.