New 20D User Needs Software Help

I just got my 20D a month ago. Downloaded images to the computer. Viewed them and they were all fine. Went back today to view. Some of the images have a black box with a question mark in it. Anyone know what this means and how I can fix it? Thanks.

What are you using to view them with??

My guess is you converted them to a tiff or some other format and the program is not recognizing them. Look at the image name and extension in the Canon program and in your Windows Explorer to see it displays it. The canon program doesn't know how to display the thumbnail so it uses the blackbox with a question mark.

Ken

i think this is because you have changed something, the name or worked on the photo iv have this happen quite a lot.
Rob.

Thanks to everyone for responding. After reading all the posts, it kind of pointed me in the right direction. I had moved them to a different program. Originally was viewing them with Canon EOS viewer utility and had moved them to another photo program. I did find them and they were all there and I was able to view them. It really is nice to have this forum to receive help from people who understand Canon cameras. Thanks again to everyone who replied. I'll take advantage of this forum more often.