I got this on my SBS 2008. To fix it, in registry editor, locate [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa3] and add a DWORD value named "DisableLoopbackCheck" type 1 in the Value data box.
A user reported this as being caused by a firewall that did not allow access to a remote content source. Adding the corresponding firewall rules fixed the problem.
From a support forum: This event may be recorded if you use two different account for "Service Account" and "Content Access Account" in Windows SharePoint Services Help Search (Central Administration > Operations > Services on Server).
The solution is to give Read permissions to the following registry key:
HKEY_USERS\…(Service Account SID)…\Software\Microsoft\Windows\CurrentVersion\Internet Settings
for Content Acces Account user.
Restart "Windows SharePoint Services Search" service.
In my case, this event occurs after a shutdown using the following command in a scheduled task: "shutdown.exe /r /f /d P:2:17". If I restart the Windows SharePoint Services Search service, the indexes are rebuilt and the error goes away.
This issue occurs when the service account for the Windows SharePoint Services Search service is configured to use the Network Service account. The search service account must not use a built-in account to access the Windows SharePoint Services 3.0 database. An example of a built-in account is the Local Service account or the Network Service account. See ME927012
to solve this problem.