HT5167: About the OS X Lion v10.7.4 UpdateLearn about About the OS X Lion v10.7.4 Update
Currently Being ModeratedAug 28, 2012 1:44 AM (in response to trapper330)
I had this issue, and what I found, is that even when logged in as an administrator, you will only have read-only acccess to the Library/Updates folder.
Try adding the admin account in 'Sharing and Permissions', make sure it has Read & Write access, then 'Apply to Enclosed Items'. Then run the update as normal.