Same thing here. I did the update this morning but it would not complete.
After reading some of these posts, I uninstalled iTunes and did a new download but got the message you're getting.
It's a little difficult to verify that you have priveleges to start system services with the choices of Abort - Retry - Ignore. What's that? And I was actually logged in at the time.
Tried all of them anyway and still couldn't get the installation completed.