To ensure that your clients are in sync with your domain controllers, you can call this command from a logon script.
Net time //servername /set /yes
Authentication requires that the system clocks of your clients be within 5 minutes of the system time on your domain controllers. If the deviation occurs on a server, then you may want to consider running this in a batch file as a scheduled task every day. Remember to use an account with the right level of user rights to run this command.http://support.microsoft.com/kb/314090