Suppressing DCOM error 10009

This is probably because you do not have enough rights. Take the CLSID given in the error message. Search the registry for this id, you'll probably end up somewhere inside the hkey_classes_root. Take the Appid and again initiate a search inside HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AppID. Right click the folder and change permissions, take ownership and give your account full control. You will now be able to change the greyed-out items.

The NTLM authentication fallback is a symptom. The real problem is why is Kerberos failing.

This sounds like a classic case of the impersonation level that is obtained is insufficient to perform the requested activity. Using delegation with Kerberos, if the machine or process that is impersonating does not have an "Impersonation" token, but instead a lower token such as "Identity", requesting Kerberos authentication to access resources on using another identity will fail.

There are four types of impersonation tokens:

Anonymous
Identity
Impersonation
Delegation

"Impersonation" allows impersonation to access resources on the same machine where the process performing the impersonation is located. In cases where the process performing the impersonation is accessing resources on a different computer than where the impersonation is being performed, a "Delegation" token is required. This typically requires the TCB privilege (Act as part of the operating system).

TokenImpersonationLevel Enumeration
http://msdn.microsoft.com/en-us/library/system.security.principal.tokenimpersonationlevel%28v=vs.80%29.aspx

Note that DCOM in Windows XP/Server 2003 the Default Impersonation Level is "Identity". This means the process may not be able access resources while impersonating another identity. You may want to experiment with the machine-wide or process level security configuration to find what works. You may find that you need to enable encryption to connect to some resources. Configuring one service the same as the other may not be an apples - apples comparison.

Connecting Between Different Operating Systems
http://msdn.microsoft.com/en-us/library/aa389284%28v=vs.85%29.aspx

Setting System-Wide Security Using DCOMCNFG
http://msdn.microsoft.com/en-us/library/ms680051%28v=vs.85%29.aspx

Setting the Default Process Security Level Using C++
http://msdn.microsoft.com/en-us/library/aa393617%28v=vs.85%29.aspx