Exchange 2007 event id 2161 and 2157

I have 2 Exchange 2007 servers in different locations and am using
Double-Take to replicate the data between them. One of them is the
production server, the other is strictly for Disaster Recovery. On
the Production server I'm getting these messages every 15 minutes:

Event Type: Warning
Event Source: MSExchange ADAccess
Event Category: Validation
Event ID: 2161
Date: 1/14/2008
Time: 10:20:30 AM
User: N/A
Computer: MailServer
Description:
Process w3wp.exe (AutoDisc) (PID=8976). Object CN=Public
Folders,CN=Second Storage
Group,CN=InformationStore,CN=DRMailServer,CN=Servers,CN=Exchange
Administrative Group (FYDIBOHF23SPDLT),CN=Administrative
Groups,CN=MyCompany,CN=Microsoft
Exchange,CN=Services,CN=Configuration,DC=MyDomain,DC=com read from
DC.MyDomain.com failed validation. Attribute: PublicFolderHierarchy.
Error message: PublicFolderHierarchy is mandatory.. Invalid data: .

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.

Event Type: Warning
Event Source: MSExchange ADAccess
Event Category: Validation
Event ID: 2157
Date: 1/14/2008
Time: 10:20:30 AM
User: N/A
Computer: MailServer
Description:
Process w3wp.exe (AutoDisc) (PID=8976). Configuration object CN=Public
Folders,CN=Second Storage
Group,CN=InformationStore,CN=DRMailServer,CN=Servers,CN=Exchange
Administrative Group (FYDIBOHF23SPDLT),CN=Administrative
Groups,CN=MyCompany,CN=Microsoft
Exchange,CN=Services,CN=Configuration,DC=MyDomain,DC=com read from
DC.MyDomain.com failed validation. Partially valid object will be
returned. Set event logging level for Validation category to Maximum
to get additional events about each failure.

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.

It's obviously something looking for the public folders on the DR
mailserver, but I don't know how to make it stop looking for them.
Does anyone have any idea why it would be doing this and how to make
it stop?
.