(English/Japanese)
The RAW development sometimes be broken in iPhoto. It is like black bar in the follwoing picture.
It happened frequently for me for a certain period of time for ORF(OlympusRaw File).
In this case, the redevelopment is possible because iPhoto has originaldata.
Select the broken image and right click. Select a menu like a "RawRedevelopment"(Sorry I don't know English Menu).
If choosing one by one is a bother, it is possible to process all chosen file even if the files includes files whose original file is jpeg.
It is uncertain whether those JPEG files change into an original file bythis processing.
Confirmed Condition:iPhoto 8, OS X 10.6.2