Apple - MacBook Pro detects external monitor but shows black screen

I had the same problem, and I think I found what causes the problem. My macbook air was detecting the display, but only thing I saw was black screen.

Either your monitor is using VGA signal even if you are using DVI cable or you are using DVI to VGA adapter in between. MiniDP to DVI only produces digital signal.

For more information check a blog post of mine.

I've had the problem as well and only by resetting my monitor am I able to get it to work.

Other posts suggesting it is something to do with the PRAM, but I've not seen the problem being on the Mac end of things. As this problem is persistent, so it seems I will have to reset the monitor each time so it recovers from the failure, but doesn't seem to address the root cause so I have yet to find a more permanent fix.

This most likely means the Mac is outputting a video mode that the screen can't display. Try reducing the resolution and Refresh Rate (in System Preferences -> Display) until you get something on the screen, then work your way up the list again. A good starting point would be 1024x768 or even 640x480.

The other possibility would be that the signal isn't arriving intact, either due to a cable/plug fault or that the screen or Mac have a hardware fault (which you can rule out by connecting the Mac to another DVI screen with the same adapter and by connecting the monitor to another computer).