So I updated to Yosemite a couple of days ago on my 2011 Macbook Pro and I have shut my macbook's lid putting it into sleep/logging out several times just like I always do... I can't recall exactly how many times, but about 1/4 to 1/3 of the time, when I open my macbook and wake it to login, it wakes up with corrupt or glitched images around the login screen... I can still type my password (even though I can't aways see it) and login. It also displays my account image correctly as well as the text in the top right corner... It just appears to be an issue with the transparency or reference to the background image that is displayed... Here are 2 photos: Any ideas? Or shouldn't I have upgraded my OS? Has anyone else seen this? What can I do?