I just had a similar experience. I was working in Aperture and all of a sudden my screen went completely black. I could hear the hard drive still working, email arrival sound effects, and so on. It seemed as if the computer were still running normally behind the dark screen.
I had to do a forced manual shutdown and reboot. On rebooting, the screen came back and all seems normal—so far.
Time to call AppleCare?
I know this is much too late, but maybe it will help someone else.
If an SMC reset doesn't fix the issue, you could verify that it is probably the Inverter that has failed.
(SMC reset is unplug all cables including power, wait at least 15 seconds before plugging power back in)
To check if it is the Inverter, when the screen goes out, but it sounds like the computer is still on. Get a bright flashlight, point it at the screen, if you can see any things that would normally be on the screen (Apple Logo while it is booting, dock, menubar, your desktop picture etc...) then it is probably the Inverter that has failed.
(newer models use LED Backlighting, and don't use an inverter like this model does)