couple of things to look at for AD auth in ESX 3

http://www.vmware.com/pdf/esx_authentication_AD.pdf
You should additionally check for:
1) Firewall
/usr/sbin/esxcfg-firewall –allowoutgoing –openport 389,tcp,out,in,LDAP We need to allow outgoing and outgoing for port 389. 2) Time.
It’s probably best to sync time with the AD server with NTP. Just configure the /etc/ntp.conf and /etc/ntp/step-tickers files with the AD.]]>