Applying a hotfix to a SQL Server 2005 failover Cluster

Hi. Was hoping to get some advice on applying a hotfix to a SQL Server 2005
failover Cluster.

The hotfix I am applying (KB933508) relates to a Maintenance Plans issue
with Server 2005 Service Pack 2. During installation I'm advised that unless
the SQL Server and other services are stopped a reboot will be required,
although I can still install the hotfix. However the installation is failing.
There are error details in the relevant logs created in C:\Program
Files\Microsoft SQL Server\90\Setup Bootstrap\LOG\Hotfix to the effect that
the 'Debug' value in registry key
'Software\Policies\Microsoft\Windows\Installer' can't be read and that SQL
Server was unable to add a user (the account under which SQL Server Agent and
Analysis Services run) to a local group (the domain group in which SQL Server
logins are contained).

Is this something simple like explicitly shutting down the services first
before applying the hotfix or is there something else going on?

Regards,

YaHozna