I have noticed with all major SP upgrades the Administrator console is
lost for a considerable amount of time during the process. Some
adminsitrators may panic during this process and restartthe server as
there is no indicator whether the upgrade is still running or what the
sitaution is as far as I am aware. Eventually it returns but it's
probably something that needs to be atleast looked at. I have seen
reports on here of failed server upgrades, and despite mine all going
fine, despite the anxious moments I am wondering whether this is what
has happened.