Yes, YOU ARE the administrator but you're not running the program AS AN ADMINISTRATOR. Thus, you must elevate Spybot S&D in order to update and immuze properly.
To run Spybot S&D as an administrator, on your desktop, right-click the Spybot S&D icon and then click on 'Run as Administrator'. Alternatively, click the Start Orb, then type "Spybot" without the quotation marks, and once you see the program shortcut, right-click and click 'Run as Administrator'. On the UAC prompt, click 'Yes' to continue.
Now, try to update and immunize.