I open up iPhoto and get an error message saying it can't located photo A (for example) it gives me "find photo" or "cancel". If I hit cancel it then goes to another error saying cannot located photo B. This process goes on for each and every photo. I'm assuming it's searching my iPhoto Library file and can't find what it's looking for. This has happened to me in the past and I just overwrote the iPhoto Library file with a previously backed up version and it worked fine up until yesterday. Any advice on how to prevent this from happening again or if this is a sign of a larger underlying issue with my Macbook or iPhoto program?