Apple has released an updated version of iPhoto ’11 version 9.0.1. The update, which is currently available within Software Update on your Mac, will fix data loss issues that users have been reporting after updating from iPhoto ’09 or earlier. According to Apple:
This update addresses issues that, in extremely rare cases, could result in data loss when upgrading a library from an earlier version of iPhoto.
For detailed information on this update, please visit this website:http://support.apple.com/kb/HT4431