Screensaver "start time" option grayed out
i am logged in to my mac as an administrator but i cannot change the screen saver idle time settings - the "start after" drop down where i can select when the screen saver turns on is grayed out. Please help - i have a macbook pro i7 (2013 model) with OSX 10.8.5.
MacBook Pro, OS X Mountain Lion (10.8.5)