This means exactly what it says. Look at the event log entries to find the location/name of each occurrence. Your directory services administrator is going to need to delete the duplicates, until there is only one. Otherwise, this error will keep repeating. Likely what happened is more than one person created the account within the replication period and the creation happened on different domain controllers. On a side note, have your directory services administrator verify replication is occuring properly on each domain controller.
K. Brian Kelley
@kbriankelley