When creating or modifying tasks in Windows Server 2008, you may get the following message after entering the credentials of the account which will run the task:

An error has occurred for task <taskname>.  Error message: The following error was reported: The referenced account is currently locked out and may not be logged on to..

If this persists after multiple unlocks, it is most likely a glitch rather than a configuration issue.  Microsoft has supplied a hotfix.