Event Type:    Warning
Event Source:    Windows SharePoint Services 3 Search
Event Category:    Gatherer
Event ID:    2436
Date:        2/25/2009
Time:        12:35:04 PM
User:        N/A
Computer:    YOURMOSSSERVER
Description:
The start address </contentdbid={f683c2eb-afc7-4154-90ce-9d75a93c6a9f}> cannot be crawled.

Context: Application 'Search index file on the search server', Catalog 'Search'

Details:
    Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content.   (0x80041205)

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

Resolution:

Follow these steps to Disable the loopback check which is causing the error:

1. Click Start, click Run, type regedit, and then click OK.
2. In Registry Editor, locate and then click the following registry key:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa

3. Right-click Lsa, point to New, and then click DWORD Value.
4. Type DisableLoopbackCheck, and then press ENTER.
5. Right-click DisableLoopbackCheck, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Quit Registry Editor, and then restart your computer.

See the following knowledge base article from Microsoft for full details on the error and another possible resolution: http://support.microsoft.com/kb/896861