One day I went to boot up my Macbook Pro. Everything seamed fine, I heard the chime and expected the Grey screen with the apple sign to appear but nothing!
Just a black screen on start up. I new the system had loaded up as I heard the chime and then, using my volume up and down keys, could hear the changes in volume.
After some research (on a PC..!) I found the following which solved the problem of a black screen on start up.
NOTE: You do the following at your own risk, you can try this as it did work for me but as always I suggest taking your mac to a local mac store and having them look at it.
I was able to fix this issue on my MacBook Pro simply by zapping the pram.
To do so:
2. Keep them held, wait for the second chime and then release the keys.
3. You should now see your screen again. Hope that helps.