Photo upload problem

lmackey

I recently took about 400 pictures over the course of a week. About 2/3 of these pictures are fine (loaded onto my computer and Picassa, I can see them when I click on them in iPhoto), but the other 1/3 are not fine. I can view these on my camera screen, as well as in snapshot form in iPhoto (they successfully loaded onto there), but when I click on them to enlarge them in iPhoto, they flash and then disappear. They also won't load onto facebook or Picasa. Should I try reloading them or do you think there's something wrong with the format of the pictures?