I recently tried to install Service Pack 4 on a clustered instance but received the following message when entering a user name and password to install the service pack on the other node in the cluster:
"The Logon account cannot be validated, verify that the username and password entered are correct."
"The Local security authority cannot be contacted"
I am attempting to move an instance name from one windows 2003 cluster to another windows 2003 cluster with the same name and ip address.
If I install another instance of SQL Server (with a different name) and Service Pack 4 it works fine.