Please ensure that ACS and AD are in time sync,ACS and AD must be time-synchronized to within 5 minutes. Both AD and ACS should be synchronized by the same NTP server. Using the command line interface on your appliance, you must configure the NTP client to work with the same NTP server that the AD domain is synchronized with.
Username/Password "to bind to domain" should have sufficient permissions to perform this task.The username you defined should be an AD user with "Create Computer Objects permission to add machines to the AD domain"
Regards,
Jatin
~Jatin