Originally Posted by zeeple
From time to time I have had a very similar problem installing OS updates on my iMac. In my case what I discovered the problem to be was that I had initiated the OS updates as another user, and the updater was not able to over ride that process despite the admin privileges of my account. Is it possible that you started installing this app as a different user? (I know this is a remote possibility, but I thought I'd share). Good luck.
No I only have one account on my Mac