Quit, remove the files “faces_blob.db” and “faces.db” from the iPhoto library. Go to your Pictures Folder and find the iPhoto Library there. Right (or Control-) Click on the icon and select 'Show Package Contents'. A finder window will open with the Library exposed.
Standard warning:
Don't change anything in the iPhoto Library Folder via the Finder or any other application. iPhoto depends on the structure as well as the contents of this folder. Moving things, renaming things or otherwise making changes will prevent iPhoto from working and could even cause you to damage or lose your photos.