(cross posting this from Apple Support communities) I'm having a problem where on cold startup or a restart, the MacBook Air screen is stuck on the Apple logo, and the external monitor shows a very light grey. This happened after upgrading to Mountain Lion and applying the SMC update. It did not happen before on Lion. (I'm not sure if it happened right after the ML upgrade, or if the SMC firmware update caused this, since I upgraded without an external monitor.) Other details: MacBook Air 13-inch, Mid 2012 Connected to an external monitor via Micro-DVI-to-DVI adapter Forcing a shutdown (by holding down the Power key) and restarting without an external monitor enters OS X normally. Power Nap is available in System Preferences > Energy Saver. Problem is consistently reproduced when restarting or starting with an external monitor plugged in. Restarts and startups are fine without a monitor attached. I can successfully connect the external display after the system's up and running. Anyone run into this problem?