The source of your problem is most likely that OS X 10.6.8 is not compatible with iPhoto 9.3. iPhoto 9.3 requires OS X 10.7 or later. Back up your photo library and try the following:
1. Trash iPhoto 9.3
2. Reinstall the latest OS X 10.6.8 compatible version of iPhoto which is iPhoto 9.2.3.
There's a good chance that will fix your problem. If not, try rebuilding your photo library. You might want to refer to one of Apple's technical articles to do this: http://support.apple.com/kb/HT2638