Are you sure that you are in full "auto" mode when you are taking your pictures? Make sure that the mode selector is set to the first red camera (without the M) right next to the little blue arrow.
If you already are in full auto, 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:
Your camera is not capable of taking 15 second exposures. Instead try putting it in manual mode, turn off the flash, take it in a darkened room, take the picture, and open the battery door while the red and yellow lights are blinking. Give it several tries, but note that the chances may be very slim for success as the shutter symptoms suggest that it is stuck open.