Can view pics on photo printer, but not camera?

I recently uploaded some pics to my computer, carefully selecting copy instead of cut to put specific pictures in my photo folder. The photo printer confirms these pictures are still on my memory stick. However, I can't view them when scrolling on my camera. It simply says "File Does Not Contain Image Data." I would like to see these pics on my camera, especially as it helps me figure dates for pics of my son. I have a Nikon D3000. Help!

Added (1). I remembered after posting this question that i rotated a lot of my pics when viewing them on my computer. Is there no way to fix the format so I can view them on my camera again?

Did you edit any of the pics?
nikon cameras are picky about the format pics are in and editing can change the format

to figure out the date, if you have windows xp or higher, right click on the picture and click properties
the exif data will tell you everything about the pic, the lens you use, if you used flash, whatever
(including date/time/gps data of WHERE you took it if your camera has a gps)

or just download a free exif viewer(google it, there's plenty of em)