try adding your current user with admin privileges to the "Distributed COM Users" users group.
- from the start menu select run and then type "lusrmgr.msc"
- next go to "Users" and then find you user account name in the right hand pane.
- open you user account properties by double clicking on the user name
- go to the "Member of" tab and click add.
- click the "advanced" button followed by the "find now" button
- Find your 'Distributed COM Users' in the list and click add.
- next click ok, on each of the open menus to close them.
- restart your PC and try the update again.
If you still have issues, try adding "administrator" user to the "Distributed COM Users" group as well.
let me know if this works for you.