Thank you for the reply
It is checked, and has always been. All photos are stored in the iPhoto library folder on my computer.
You might be right about the thumbnail, though it is hard to tell since the photos at hand are taken with an iPhone 4. I was not able to find any missing photos in any events taken with my proper camera. I am able to zoom into the photo while the error message is displayed though?
I do keep bakups of both the Library file itself and standalone photos, but either way I find it absolutely unacceptable that iPhoto just looses photos by itself ...
Any other suggestions?
Edit: I might add that my library exceeds 10K photos if that puts me in a greater risk?