Same problem here. Happens on about 10% of my photos.
Here's a link to an image that goes black when edited in iPhoto 09.
http://dft.demo.letsoftware.dk/IMG_0015.jpg (don't click unless you really want to try it as it's a big download).
The image is from a Canon 8800F scanner. 95% of the photos are ok - they are all about the same size (some bigger, some smaller), so it doesnt appear to be a size/dimension issue.
If I click the "effects"-button in iPhoto the full size image will however show up, but when adjusting using the edit controls nothing happens to the image.
The graphic card is a NVIDIA 7600GT (some other users have indicated that it only happens with NVIDIA cards)...?
Any ideas? (and I've tried reinstalling, deleting prefs and plists and all the usual stuff)... 🙂