I am a new iPhoto user. I have successfully downloaded pics from my camera, edited them, then tried to export. That failed (I'll deal with that later), but now while I see the thumbnails in the library and the album, I can't see the actual pictures at all. For example, if I try to expand as if to edit, the screen stays blank with a spinning circle of death. What happened? How to resolve? (I could re-download from the camera as I did not erase, and re-edit, but the same thing could happen again). many, many thanks.