Photos appear blank in iPhoto on the Mac

At home I've got an iMac (2009 version). We run iPhoto on it to manage our family photos - the photo library lives in a shared directory - both of us have separate accounts on the computer but we want to share the same photo library. Occasionally we run into a problem where you can see photo thumbnails in iPhoto, but when you double-click to open the photo, it goes blank and you just see a black screen where the photo should be.

After some searching I managed to find a few other people who'd run into the same problem. The solution is to rebuild your photo library in iPhoto. Exit the application, whilst holding down the command and option keys on the keyboard, restart iPhoto. You will see a prompt asking which parts of the library you'd like to rebuild. For me, examining and repairing iPhoto library permissions is what's worked.

If you want to know more you can find an Apple support article here.