H90 severe overexposure

My H90 has suddenly started to severely over expose - daylight photos are completely blown out, giving an almost white screen. Indoor shots in low light are ok but there are coarse Moire circles everywhere. Movies are fine. I just found out that if I switch on and take a shot a maximum telephoto, photos are fine  and are ok across the zoom range, but if I switch off and back on I get the blown highlights. Has anyone got any idea what is going on and if I can cure this? I've tried a re-set and taken the battery out for 24 hrs.