Here's a couple troubleshooting steps to try:
* Try pressing the INFO button a couple times to see if it will get something to display on the screen. This changes what is displayed on the screen while shooting photos and one of the modes is just a blank screen (though I believe it normally would go back to a default screen when you turn off and on your camera anyways).
* If that doesn't do anything, try pressing either the playback button or the MENU button to see if either of those do anything.
* Shine a flashlight on an angle to the screen and see if you can make out an image at all. If you can, this would indicate a problem with the backlight on the LED screen.