Why is this happening? Has any one ever experienced anything like this before? Some windows stay dark on my external monitor and some come good after I let go of the cursor after dragging..
Check this thread out: https://discussions.apple.com/message/16608477
To quote: "...opening Display in System Settings, and choosing calibrate under Color seems to have fixed the problem." I don't have my external monitor with me at the moment, but wil check when I'm at work tomorrow.