Problem booting CentOS 5.2 machine

[John Aldrich <jmaldrich yahoo com>]

I have a CentOS 5.2 machine that is refusing to get past starting the 
System Message Bus. This machine is tied into an Active Directory as a test 
mail server. A little Googling shows that it's somehow related to being 
unable to talk to the LDAP server. How do I figure out what's causing the 
problem? Yesterday before rebooting the server, I downloaded and installed 
a newer version of NMAP on it, and suddenly yesterday, shortly after I 
rebooted it, it won't finish booting.  As I said, I looked for an answer on 
Google and found that it's tied into LDAP, but I'm not sure 1) what is 
causing the problem and 2) how to solve it.

Can someone here please provide some help? I'm not exactly a linux newbie, 
but I am new to tieing linux into Active Directory.