kdesktop_lock won't authenticate against AD

[Marcelo Magno T. Sales]

Hi,

My FC5 / KDE box is part of a Windows 2000 domain. I've configured it to 
authenticate login credentials against Active Directory and it's working 
well. However, when I lock the desktop (manually or via password protected 
screen saver), I can not unlock it if the logged in user is an Active 
Directory user. 
kdesktop_lock fails with the following message:
"Cannot unlock the session because the authentication system feiled to work; 
you must kill kdesktop_lock (pid_of_process) manually"

A local user can unlock the desktop without problems.

Any idea about what may be causing this?
Here is may pam configuration for kcheckpass (/etc/pam.d/kcheckpass):
#%PAM-1.0
auth       sufficient  pam_timestamp.so
auth       include     system-auth
account    required    pam_nologin.so
account    include     system-auth
password   include     system-auth
session    include     system-auth
session    required    pam_loginuid.so
session    optional    pam_timestamp.so
session    optional    pam_selinux.so
session    optional    pam_console.so

Also, /usr/bin/kcheckpass permisions are set as 4755.

Thanks,

Marcelo