Try this: make a temporary, backup copy (if you don't already have a backup copy) of the library and try the following:
1 - delete the iPhoto preference file, com.apple.iPhoto.plist, that resides in your
User/Home()/Library/ Preferences folder.
2 - delete iPhoto's cache file, Cache.db, that is located in your
User/Home()/Library/Caches/com.apple.iPhoto folder.
Click to view full size
3 - reboot.
4 - launch iPhoto and try again.
NOTE: If you're moved your library from its default location in your Home/Pictures folder you will have to point iPhoto to its new location when you next open iPhoto by holding down the Option key when launching iPhoto. You'll also have to reset the iPhoto's various preferences.
If that doesn't help log into another user account on your Mac and see if iPhoto will work as it's suposed to there. If it does then the problem lies with your account. If iPhoto crashes in the other account a reinstall of iPhoto is indicated.
To do so you'll have to delete the current application and all files with "iPhoto" in the file name with either a .PKG or .BOM extension that reside in the HD/Library/Receipts folder and from the /var/db/receipts/ folder,
Click to view full size
Then install iPhoto from the disk it came on originally and apply all appropriate updaters.