This may or may not be a graphic problem.
- Clear private data/cache
- Clear JAVA Cache
- Check if your video card is working properly/plugged in all the way
- Check if there is new drivers for your video card/update them.
All of you guys are wrong, if a black screen is loading, it's because of the server.
If you wait for like 25 seconds, it'll load.
The new server is really glitchy, especially the new tiles and it's physics.
not necessarily... ive gotten black screen in SP and such
I know how to fix it...
It worked for me, but it will erase all your data, worlds, texture packs.
All you have to do is go to start, run, type in %appdata% and then delete your .minecraft and java folder.
Then, go to minecraft.net and play it in browser and then download it and it should work, if not, i dont know what to tell you.  [>>-i>]
I just built a new computer with an i5-2500K processor, windows 7 home premium, and an nvidia 470 video card. I have the latest version of java, latest version of the client, and up to date video card drivers. I log on to my friends SMP server, (he generated a new world about an hour ago), and after 5-10 minutes of playing, minecraft's screen goes black and I have to force close and come back. I can restart, play for another 5-10 minutes, then it black screens again. I've tried clearing the .minecraft folder in %appdata% as suggested, but it didn't solve the problem.
EDIT: I think I figured out the problem; My computer resolution is 1920x1080, so I was manually increasing the size of the minecraft window (dragging the corner of the box). When I ran at the default game size, I had no problems. When I noticed I had been running at the small default size, and went to increase the window size after a half hour of playing, the game froze (black screened) immediately after attempting to increase the window size.
EDIT2: Guess it's still just seemingly random, had a few more black screen freezes with the default window size.