Displays icons but won't register pictures

First make sure that you accidentally didn't turn off the screen by repeatedly pressing the DISP button to cycle it on and off. If that didn't fix it, and if your camera is less than 1 year old, call 1-800-OK-CANON to arrange free warranty repair.
If your camera is more than a year old, a stuck shutter is another common failure mode for digital cameras. The symptoms of a stuck or "sticky" shutter are very similar to CCD image sensor failure. The camera may take black pictures (for shutter stuck closed), or the pictures may be very bright and overexposed, especially when taken outdoors (for shutter stuck open).
To confirm a stuck shutter, put the camera in any mode other than "Auto", and turn the flash OFF (you don't want to blind yourself for the next step). Next look down the lens and take a picture. You should see a tiny flicker in the center of the lens as the shutter opens and closes. If no movement is seen, then you likely have a stuck shutter. If so, please see the following for further info and a simple fix that may help: http://camerarepair.blogspot.com/2009/05/simple-fix-for-stuck-shutter.html