For some reason I frequently encounter these DCOM errors on servers running SharePoint Services:

Log Name: System
Source: Microsoft-Windows-DistributedCOM
Date: 25.05.2008 15:50:23
Event ID: 10016
Task Category: None
Level: Error
Keywords: Classic
User: NETWORK SERVICE
Computer: server.domain.com

Description:
The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID {61738644-F196-11D0-9953-00C04FD919C1} to the user NT AUTHORITYNETWORK SERVICE SID (S-1-5-20) from address LocalHost (Using LRPC). This security permission can be modified using the Component Services administrative tool.

If you see an error like this follow these steps to fix it:

1. Figure out which COM Server application that is the problem. Run this command:
   reg query HKCRAppID<COM Server GUID from Event log entry>
   In this case the command would be:
   reg query HKCRAppID{61738644-F196-11D0-9953-00C04FD919C1}
   HKEY_CLASSES_ROOTAppID{61738644-F196-11D0-9953-00C04FD919C1}
   (Default) REG_SZ IIS WAMREG admin Service
   LocalService REG_SZ IISADMIN
   AuthenticationLevel REG_DWORD 0x6
2. Open up the Component Services tool; dcomcnfg.exe
3. Expand Component ServicesComputersMy ComputerDCOM Config
4. Locate the failing component in the list, either by name or GUID, and select Properties.
5. Open the Security tab.
6. Depending on your error select Launch and Activation Permissions (as in this example), Access Permissions or Configuration Permissions.
7. Add the required permissions:
   
8. Hit OK twice to return to the Component Service tool.

The error should now be resolved.