Why does my digital camera always over-expose?

My Pentax Option S10 has started over-exposing after about 3 years good service. I did not attempt any adjustment which might have caused a change. I cannot find any adjustment, using the manual, to get it to give a normal picture. The effect on a picture taken indoors in moderate light (flash off) is that the image is undetailed white on the better lit side with a pale faintly detailed image on the less illuminated side.
With the flash on, and out of doors in daylight (no flash) there is a featureless white image. Existing images (about 1400 of them on the card and 6 on the resident memory) are unaffected.
Any advice would be gratefully considered.