On my 2011 15" Macbook Pro I am having several problems with my desktop picture. First, I am unable to set an image to be a desktop picture from the internet when I double click. Is this normal or is there a way to do it? Also, when I do set a desktop picture sometimes when I shut it down and start it back up, it changes back to the default background and I have to redo my desktop picture. Any help would gladly be appreciated! Thank you!