Apple has updated iPhoto for Mac OS X to version 9.3.1. The update includes several bug fixes.
- Addresses a problem during the migration of albums from MobileMe Gallery that may cause photos to be moved from their original events into a new event called "From MobileMe"
- Fixes an issue that in rare cases could cause iPhoto to hang when upgrading libraries
You can update iPhoto by going to System Preferences > Software Update or you can grab the download directly from here.