I had the same problem. I tried every bit of advise above, but unfortunately nothing worked for me until I stumbled upon a seemingly unrelated article. For this, I'm going to hope and assume that you have backed up your photos somewhere.
The trick is storing your photos outside of the iPhoto library.
If they're not already, transfer your photos to your Mac's Photo folder (in Finder). Once transfered, this is the point where you should organize your photos if you need to.
At this point, you should either delete the corrupted photo folders in iPhoto or create another library in iPhoto, so you dont create duplicates of all your pics. Once that's done,
Open iPhoto. Go to Preferences > Advanced > and uncheck the first check box "Copy items to the iPhoto library"
Unchecking this box lets iPhoto reference the photos on your computer, but not transfer them iPhoto, which is where the problem is.
You can now go to Import Library, and begin "importing" to iPhoto.
A further explanation, as well as other helpful tips can be found in the article at:
http://www.macworld.com/article/1143828/referenced_library.html
Good luck!