I have a canon powershot sx200 IS and I recently went on vacation and took a lot of pictures using teh SD memory card provided with the camera. For some reason, after almost filling the card I received a memory card locked error. I checked the card, it was not locked. I even tried in another camera and same error. So I got a new SD card, took more photos and then all of those photos were erased. I could not find them when reviewing on the camera, another camera, or even with a USB card reader. Any idea why they were all erased?

The likely reason this keeps happening is that these cards weren't formatted in the camera when you first got them. However, don't do so just yet as formatting also erases the card. If you are using a memory card, take no more pics until you've recovered the photos, take the card out of the camera. This is to reduce the chance of you overwriting some of your "lost" photos. There are many good freeware photo recovery software options that are available to help you recover your photos. This blog article reviews and outlines several of the better ones. Now AFTER you've recovered the photos, format the cards IN THE CAMERA USING THE CAMERAS FORMAT FEATURE. Look for it, it's located under the "tools" menu (look for the item stating the card's memory capacity). This should rejuvenate both cards, and prevent reoccurrence.