I have the same problem, my card is definitely not locked. I was using the camera to take pictures on thanksgiving. Put it away to eat, after dinner I turned it on (never took out the card) and I got the memory card error. I tried three other cards All previously formatted by the camera, they all come up memory card error. If I switch to play the photos it says card locked. I have tried to format the card('s) through the camera but format is grayed out. I can get the pictures off the SD card on my computer without a problem. I have tried to format an SD card on my computer, it formats fine (FAT32), still memory card error when I put it in the camera. I have gone the canned air route and done the toothpick trick (it was not stuck). I have been reluctant to send it to canon hoping to find a quicker solution, before Christmas. Besides the warranty expired two days before Thanksgiving, timing!!! But everyone gives the same answer- check the lock button on the card.