This happened to a friend and while some of her photos were backed up, there were problems with the backup. Problems with backups are not always apparent until you decide you need to restore some files then find out what you thought was backed up isn't. If this happens because something else went snapfoo your options rapidly dwindle.
So how do you access images stored in the iPhoto application when the application malfunctions? iPhoto stores the images in folders under the Pictures master folder. The iPhoto application resides within the Pictures folder and acts to retrieve images in the Pictures subfolders. However, it is possible to locate the hidden subfolders. Let me explain how I did this on my MAC. A similar process should work on a PC.
Even if you store your photos using iPhoto, you probably have one or more images stored elsewhere on one of your hard drives, maybe even the computer's internal hard drive. Enter the file name in the Finder search window and it will display the folders path of the file for each instance of the image. You may have may but probably only one in the Pictures folder. If several, check each one until you find a file path that includes iPhoto Library. In this example, I have searched for a file named "0444 Alignments" and found four instances on my hard drives. Only one of the files with this file name is located in the iPhoto Library.
While I cannot open the iPhoto Library if it is not working, I can open the 'Originals' folder. In it are a series of subfolders by year with all of my photos uploaded to iPhoto.
Once you have come to this point, you are on your own. Happy recovery!!