note of exclamation at image in storyboard

I see at some images in the timeline a note of exclamation. What do I have to do and how to solve it?

You can click on it, to see what FotoMagico is complaining about.

after rescaling… the app crashes and i lost the whole diashow including thumbnails

755 images before tomorrow i have to deliver

Sorry to hear, that the app crashed and you lost your slideshow. I looked into your crashlog you sent to us and it seems that the app ran out of memory. Was the crash happening as the resizing of the images was in progress?