I've researched threads all over and have chatted with Apple Support multiple times but still have not been able to resolve this issue. Here's the situation: I've had my MacBook Pro Retina, newest 13in model for about 3 weeks and the other day I tried to change the wallpaper. When I turned on my computer again the next day, I go onto the login screen and enter in my password. The progress bar proceeds to load to boot to my desktop but it doesn't get a chance to complete before the computer automatically restarts, chimes, and then the blurred login screen changes, reverting to the old default (when it should match with the desktop wallpaper after logging in). This problem doesn't affect my performance or any other tasks on the notebook but I just find it REALLY annoying. I've tried resetting SMC/PRAM, even did a clean install erasing the disk and reinstalling Yosemite like the tech support told me to. I sent in the computer for repair and all the service center did was just restore the OSX software (which I already did). My computer is coming back in on Monday and I'm afraid the issue will still be there. I was suspecting a hardware issue but diagnostic tests and disk utility repair/verify have all come back negative. Does anybody else have this problem? I've attached a video on youtube to show what I mean. Any insight would be appreciated. Thanks!