If you run Exchange 2007 SP1 with an antivirus program like Trend Micro ScanMail 8.0, the following event may occur in your eventlog:
Event Type: Warning
Event Source: MSExchangeIS
Event Category: Virus Scanning
Event ID: 9874
Date: 8/4/2008
Time: 8:34:47 AM
User: N/A
Computer: %
Description:
Unexpected error 0×80040109 occurred in “EcProcessVirusScanQueueItem” during virus scanning. Mailbox Database: %/cn=Microsoft Private MDB