Mac OS X - Energy Saver preferences won't save

Log in as an admin, run the following commands from Terminal:

sudo rm /Library/Preferences/SystemConfiguration/com.apple.AutoWake.plist
sudo rm /Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist
sudo rm /<user>/Library/Preferences/com.apple.systemuiserver.plist

Reboot. The next time you set your Energy Saver preferences, the settings should stick.