When iPhoto '11 crashes after importing photos and videos, they are gone. How can I retrieve them?

iPhoto '11 randomly crashes after importing/editing/organizing photos and videos. When it does, photos and videos that I've been working on are gone. Pictures taken with iOS devices can be retrieved if they are still in Photo Stream, but videos are gone. Is there anyway I can retrieve photos and pictures that are not saved before iPhoto crashes? Also, is there anyway to prevent it from crashing? It seems iPhoto '11 is doing this since the day 1 I started using it. Thank you.