Sounds as though the CCD (image sensor) has developed a fault or has been damaged, this possibly by being allowed to point at the sun. There is nothing you can do about this as it requires internal investigation, all this being said of course with the assumption that you can still get a menu on the screen, as if you cant then the LCD could have developed a fault OR been damaged. If the LCD is at fault, an easy test is couple the camera up to your TV and check if you can see what would normally be on the LCD.