Info: Had my MBP 13" for almost 2 weeks now. Running Mountain Lion. Problem: Last night (13-14 hrs. ago) I changed my desktop wallpaper from the default one to some wallpaper I found on the internet. Changing was a breeze. Nothing came up. But, just this afternoon, I decided to take a look at the other wallpapers in system preferences>desktop and screensaver but it kept on freezing/not responding (had to force-quit every time). I googled the problem and found things such as: deleting com.apple.desktop.plist (from Library>Preferences) and com.apple.systempreference.plist (from Library>Cache) both from the library which I did and worked like a charm at first When I rebooted my MBP (it was included in the steps after deleting the files), I found out the wallpaper I took off the internet is gone and once again replaced by the default (which I don't like that's why I changed it in the first place). I opened the system p>desktop and screen saver once again and poof it's not freezing anymore BUT when I selected an iPhoto folder from the selection, it started freezing again!! This problem is really driving me nuts. I just want to change my goddamn wallpaper. Why does this have to happen?? CURRENT SITUATION: Desktop wallpaper back to default and "system preferences>desktop and screen saver" freezing once again (the original problem). Meaning to say, I've already deleted the files above (but I think they get replaced right back anyway) but I'm, again, stuck with my original problem.