Apple has released iPhoto 9.0.1 which addresses issues that, in extremely rare cases, could result in data loss when upgrading a library from an earlier version of iPhoto.
iPhoto 9.0.1 is available via Software Update and also as a standalone installer.
More info and download link (33.87 MB) here.
Detailed information on this update here.
[Thanks to MacDailyNews Reader “Jay in DC” for the heads up.]