I am having a terrible time trying to get my sugarCRM CE 5.5.1RC3 version to work in authenticating AD users in a 2K8 server. I seem to get the following errors in the log file.

03/16/10 10:37:57 [1228][-none-][FATAL] [LDAP ERROR][49]Invalid credentials
03/16/10 10:37:57 [1228][-none-][FATAL] SECURITY: ldapauth: failed LDAP bind (login) by helpdesk, could not construct bind_user
03/16/10 10:37:57 [1228][-none-][FATAL] SECURITY: User authentication for helpdesk failed
03/16/10 10:37:57 [1228][-none-][FATAL] SECURITY: User authentication for helpdesk failed
03/16/10 10:37:57 [1228][-none-][FATAL] FAILED LOGIN:attempts[1] - helpdesk

I have the following settings configured for LDAP in sugar. am i missing anything or doing anything wrong. Thank you.

Server: server.companyname.com
userDN: dc=companyname, dc=com
Bind Attribute: userPrincipalName
Login Attribute: userPrincipalName
Portnumber: 389
Authentication: ON.
username: CN=administrator,CN=Users,DC=companyname,DC=com
password: correct.