FIX: iPhoto pictures NOT available when changing desktop background / screensaver
If you have recently upgraded to iLife 11 or moved your iPhoto pictures folder to another place and there is no arrow besides the 'iPhoto' line in the desktop & screensaver preferences pane, all you have to do is to remove a file from your home folder. First, QUIT system preferences if you have it running, then open terminal.app and type
That's it! Now when you run desktop & screensaver preferences, iPhoto will be available again with all your photos !!