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I updated from 10.8.1 to 10.8.2 for my MacBook Pro Retina with my external 27" Thunderbolt display. When I connect to my Thunderbolt display both screens are black. I can only see my mouse pointer and sometimes little boxes of display. Any idea what's wrong?

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The solution explained in this Apple Discussions thread worked for me.

  1. Delete /Library/Preferences/
  2. Delete ~/Library/Preferences/ByHost/
  3. Reset NVRAM.
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