Do the menus show up on the display, or is it only a problem with photos taken?
Press the display button (DISP) to make sure your display is turned on if menus don't show up either.
If the photos are black and the menus are working, it's probably an imaging sensor failure (or one of the supporting components), with no signal being generated by the CCD.
I'd check to make sure you're in Auto Mode (in case you have a shooting mode set to manual with settings that are causing an underexposed photo).
See page 21 of this manual for changing shooting mode: