Why does my photo turn in to a white after using the enhance tool?

Question

When I'm using the Enhance tool on certain photo's, the photos turn pure white! This has only started recently. It even does this on old photos that I have used the Enhance tool on previously. If I use the Undo option, my photo will return to usual, but at the moment my Enhance tool is broken!
I have tried repairing permissions and the database but it did nothing to solve the problem
I am using iPhoto 11 on Lion. Everything is up to date.
Please help.

Answer 1

Try this:  launch iPhoto with the Option key held down and create a new, test library.  Import some photos and check to see if the same problem persists. If you get the same problem in the new library 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. 
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3 - 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.
OT