Had a similar issue (screen would just go black again a random interval after wakeup from sleep and have to login again). Resetting the system management contro

Had a similar issue (screen would just go black again a random interval after wakeup from sleep and have to login again). Resetting the system management controller did the trick for me: http://support.apple.com/kb/HT3964 http://support.apple.com/kb/HT3964