Hi George,

> They are all configured the same.

They can't be. If they are configured the same they would behave the same. Something is different among these.

Have you checked if regular domain users do have networking login permissions?
Have you turned on auditing in the Local Security Policies?
Can you impersonate the user on one of these machines and access the COM server locally?
Have you checked the event log on the client and the server?
Have the user permissions to all files required? Use PROCMON from Sys (http://msdn.microsoft.com/en-us/library/ms809327.aspx)
Here's a guide how to configure DCOM properly: http://www.codeproject.com/KB/COM/dcomcnfg.aspx