I've been experiencing this problem recently on my MBP 9,2 (13 inch, mid 2012) running OS X 10.10.2. Every time I plug in an external display (connected to a Mini DisplayPort VGA adapter), the screen on my laptop turns black, and no output appears on the external display. The laptop itself appears functional: the screen is still on, and while no keyboard input is taken, the caps lock light still activates. Even when removing the adapter, the display does not revert back to the desktop, always requiring a hard restart of the whole system.
I've already tested it on multiple monitors which ruled out a problem with the particular monitor I'm using. I'm currently unable to test my adapter on other devices or try a different adapter on my laptop until after the weekend. I've already updated OS X and even reset the SMC; none of these resolved the problem. I have doubts that a software update caused the problem, because it first happened on the same day when I was able to successfully show a presentation in the morning. The adapter itself is made by Apple and is almost a year old, and I'd rather not go back to the shop to buy another unless I'm completely sure that it's really the cause of this problem.
Thanks for any help or insights.
I've already tested it on multiple monitors which ruled out a problem with the particular monitor I'm using. I'm currently unable to test my adapter on other devices or try a different adapter on my laptop until after the weekend. I've already updated OS X and even reset the SMC; none of these resolved the problem. I have doubts that a software update caused the problem, because it first happened on the same day when I was able to successfully show a presentation in the morning. The adapter itself is made by Apple and is almost a year old, and I'd rather not go back to the shop to buy another unless I'm completely sure that it's really the cause of this problem.
Thanks for any help or insights.