Linux Mail Server Setup and Howto Guide

okay so i have AD setup on Windows Server 2008r2 and multiple servers running various versions of CentOS 5 (5.4, 5.5, etc).

i followed the directions from this guide:

http://www.linuxmail.info/acti…..e-sign-on/

i finished everything and checked the credentials with kinit which seems to be working. however, when i try to log in, it takes a really long time to come up with the password prompt, and after i enter the password (and having it sit again for a really long time) i get the following message:

Connection closed by address of server

i saw this little warning at the bottom of the tutorial that says:

The version of sudo that comes with RHEL/CentOS 5 does not work with non local user accounts. While this is not yet fixed, use the sudo rpm package for Fedora 8.

i tried to update this but it sends me through dependency hell. how do i update this and if i do update this, will it fix my login issue?