When I want to edit a photo via iPhoto, it disappears. iPhoto displays a black screen with an exclamation point. I have already tried to rebuild the thumbnails, repair permissions and repair the database without any results.
This happens when you move or rename the original photos manually. iPhoto can not find the original files.
Note that: you should never intervene yourself in the iPhoto Library folder.
More information on this link: http://support.apple.com/kb/HT1261?viewlocale=en_US.
Thanks to Sanspseudo for this tip