If you have more than one domain controller and are trying to examine why an account keeps locking out (for example, after a password change), you can download a tool from Microsoft called LockoutStatus.exe. This tool will help you analyze which Domain Controller the lockout happened against if there is more than one DC. It will also list the time it happened so it can help speed up the process of examining the Security logs in the correct DC’s event logs.
The tool can also be used to unlock accounts easily. You must specify the name of the domain account that you are searching for. [more]
Further information can be found here: http://technet.microsoft.com/en-us/library/cc738772%28WS.10%29.aspx