Hi,
Last year I tried to get this working on a CentOS 4 server, but I could not get it running.
I used this module at the time: http://adldap.sourceforge.net/wiki/doku.php?id=mod_auth_ntlm_winbind
I spent some time trying to figure out what was the issue, but eventually I just gave up. I believe I had some problem on the Samba config somewhere...
My current job is Linux only so I never tried this again, maybe it would work under CentOS 5, it might be worth the try...
HTH, Filipe