Here's the actual event. It occurred three times for the same server within 1 minute and 4 seconds last night. Some nights it starts twice and others only once. Other mailbox archiving tasks on the same EV server only seem to start once, but this Exchange server has by far the most mailboxes.
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Event Type: Information
Event Source: Enterprise Vault
Event Category: Archive Task
Event ID: 3156
Date: 12/12/2007
Time: 2:25:15 AM
User: N/A
Computer: BELARCHIVE02
Description:
Start to process the Exchange system BELCCR02.
For more information, see Help and Support Center at http://evevent.symantec.com/rosetta/showevent.asp