You are using the Enterprise product? Normally for a service pack installation the general rule is to disable virus protection. Microsoft offer free support for service pack installation so they would be the best people to advise you on this, however I would defer to any Enterprise experts here who hopefully will post soon.
I believe that barefoot138 is referring to the McAfee firewall that runs on Windows.
Well I haven't heard of a firewall blocking such operations but I guess it's possible. So how does he disable it?