Hello when i pressing power button on my macbook pro, my macbook is turning on but stay on black screen about 30 seconds then apple logo and user/pass and then yosemite running without any problem. i haven't this problem and my macbook was booted about 15 seconds. what is this problem and how can i Resolve it? i using from clean my mac for uninstall my application and clean my mac scan my system automatically. i think clean my mac removed or damaged to part of system. because after scan ituneshelper removed from login items and i restore it from itunes contents>macos. Please help me, thank you.