Hey there,
I just got a mail from my provider that the cronjob has been switched off due to problems. When I checked it manually it leads to 404.
I have no idea why this happens every x weeks. I did not even touch the site since the last time it happened.
I am afraid the moment the cronjob works again, the problem with the disappearing images restarts... Maybe you remember:
http://stackideas.com/forums/images-gone-after-cronjob