Why won’t iPhoto open my iPhoto Library any more?
Unfortunately, I'm not super familiar with the inner workings of the library file.  You can copy the masters out and reorganize them into a new library so that your pics aren't lost:


open a terminal window
type mkdir ~/Desktop/RecoveredPicsEnter.  This creates a new folder on your desktop where your recovered masters will live.
type (but do not hit enter) find make sure to leave a space
drag the iPhoto library into the terminal window.  This has the effect of pasting the path to the library.
It also put an extra space at the end of the path, delete it.
type /Masters immediately after the path, make sure there's no spaces between them
NOW you can add a space and past the rest of this into terminal: -type f -exec cp {} ~/Desktop/RecoveredPics/ \; 
Hit Enter
Now you can head over to the Finder and check out the contents of the RecoveredPics folder that's on your desktop.  If you're satisfied with the contents, you can drop the folder on iPhoto and create a new library from these.  


Let me know if this is helpful!