FWIW, my daughter has a similar issue with a Kodak EasyShare C182.
When attached to a MBP or iMac, the thumbnails are fine up until the time of the first *.MOV file. From then on, sorted by date, every picture and *.MOV file appears as a blank box, and when I try to import any picture --- before or after --- the file format (*.jpg) was not recognized.
The pictures/files are not an issue: they were readable on a Fusion/XP machine on my MBP. I moved them to a USB drive and from there I was able to add them to iPhoto '09 without any issues. So it's not the camera, the pictures, or my hardware.
The problem is located somewhere between the camera, drivers, and iPhoto '09. And I think it was caused by a recent software update, because we didn't have a problem with the last download on May 16th (or so).
I did not try removing the Caches & Preferences, as suggested, partly because I'm hesitant to delete things I don't understand. But also because if the problem is happening on more than one Easyshare, it needs a better fix.