Q: iPhoto Crashes after Faces Clicked?

Try rebuilding the library:

iPhoto Library rebuild

More information:

https://discussions.apple.com/message/12868895#12868895

If rebuilding does not work, you could also drag the actual application to the trash and redownload through the App Store. This will not delete the photo library, and it will generate a fresh version of the application on your HD, as well as a new preference list, although Eric's article is where you should start.