pam_mount get the credential at logon. He take the user name and password. This two are the same on AD and samba, that why it is working.
The problem is that centrify and pam_mount dont share this information apparently.
The problem with fstab is that you need to save you credential when pam_mount just get them "on the fly" to mount the CIFS. Nothing is stored and when user log out its unmount.
I know that centrify and pam_mount both madofy pam.d/session-auth and other. And i may suspect the problem id from that.
Cause like i said, its working on the terminal but not on the "classic way" :(