Since I upgraded my domain to Windows Server 2008, the LDAP authentication in Bugzilla is failing for certain users (invalid credentials). Is there a fix for this? I am using Bugzilla 3.0. Please advise.
Use a network sniffer like Wireshark to make a capture of the LDAP traffic. If it is tunneled trough SSL get also the private key of the LDAP server or use a LDAP proxy. LDAP is pretty chatty and you will find easily why it denied the request.
EDIT: Try to isolate the problem. Check the Windows logs. Try to connect with a different LDAP client using the same credentials as that user. Try to bind to the LDAP server using a small PHP script. You can try phpLDAPadmin to see if you have the same problem.