1. I re-installed iPhoto from original Mac Applications Install Disk. Couldn't skip this step because my installed iPhoto wouldn't even be recognized by the upgrade made on step 2;
2. Downloaded and run latest available iPhoto version from Apple website, which was version 9.1;
3. iPhoto launched perfectly and immediately pointed to another available upgrade: version 9.1.1;
4. Made the new upgrade. iPhoto now works perfectly. Good news: my Library was intact.