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If that didn't work, then we can rebuild your iPhoto Library and see if that works or not.. Rebuild iPhoto Library
If that didn't worked then rebuild your iPhoto Library with this application, iPhoto Library Manager (just try the trial version) : http://www.fatcatsoftware.com/iplm/ Please follow the instructions in here to rebuild your iPhoto Library with iPhoto Library Manager : http://www.fatcatsoftware.com/iplm/Help/rebuilding%20a%20corrupted%20iphoto%20library.html
Let me know if that didn't work too, so we can create a new iPhoto Library and extract the photos from your old Library to the new library.