I suspect there's someting related to samba and winbind configuration.
Here's the /etc/samba/smb.conf.
Do you think there some statement which can introduce long delays?
[global]
workgroup = BSI
realm = BSI.NET
server string = %h
netbios name = bsipprd0032
security = ads
encrypt passwords = true
password server = *
obey pam restrictions = yes
preferred master = no
# printcap name = cups
disable spoolss = Yes
show add printer wizard = No
idmap uid = 10000-20000
idmap gid = 10000-20000
# comment the following string to strip the domain part of the domain\username - advanction 14/02/2013 - PARI
winbind use default domain = Yes
template shell = /bin/bash
use sendfile = Yes
# printing = cups
winbind offline logon = yes
winbind refresh tickets = yes
winbind enum users = yes
winbind enum groups = yes
auth methods = winbind