When browsing picture folders, from time to time you see that some thumbnails were not generated. Maybe 10% of them. Instead, a stricken-through blue polaroid icon appears. Double clicking on it loads the picture correctly, so there must have been a problem with the generation of the thumbnail (maybe the server was overloaded at that moment?).
I think that missing thumbnails should be regenerated the next time a user lists that picture, or by just refreshing your browser.
Customer support service by UserEcho