Hi everyone, I'm new here, and I have a problem I've never encountered before.

I've had a Canon Powershot SD 850 IS for about a month now and use an ATP brand SD 2GB memory card. Midway yesterday (after taking about 200 photos), I did some reviewing and found that some of my images were "unidentified" and now showed up as small thumbnails. I was confused because they had shown up fine upon immediate inspection. Why were they suddenly corrupted? I kept on taking photos, and everything seemed fine. Out of the 200ish photos I took last night, only a few of them showed up as unidentified later. It just seems so random: two from 11AM, seven from 3PM, one from 11PM...you get the picture. When I uploaded them onto my computer today, the thumbnails were fine, but when I actually tried to view them, they showed up halfway and mixed with other photos. All of the videos I had filmed yesterday were fine though.

Can anybody tell me what's wrong here: my camera or my memory card? Or is it my own fault? I never had this problem with my old Canon, and I don't think I pressed anything when taking those now-unidentified photos. I've never used ATP before, though, maybe that's why. I just want to know how to prevent this from happening the next time I take photos.

Also, are there image-recovery programs that don't require memory card readers? Even though I know most people use readers, I'd like to know if my photos can even be saved before I buy one since I'm perfectly satisfied with using a USB cable.

I think that about covers it. Any help is appreciated!