your damaged image probably is from your most recent import. I'd suggest to try to open the master image files from your recent import in another program e,g, Preview.
If your library is managed . the masters included in he library package, you will find them by ctrl-clicking the the Aperture library package in the Finder and selecting "Show package Contents".
Then open the "Masters" folder. This folder is organized chronologically by the import date. So your corrupted image most probably will be in the folder with the most recent date.
Browse this folder and try to open the images in Preview (or your camera's raw converter, if you are shooting raw).
If you cannot spot the culprit this way, then you will have to try to find the corrupted image by creating previews for subsets of your images in Aperture.
- Turn on the Activity Viewer (Window -> Show Activity) to see which images Aperture is processing.
- Select some of your recent import, ctrl-click the images and select "Update Preview".
If Aperture crashes again, you will know the corrupt image is one of the currently selected.
Restart, and try the same for half of the selection, until you know which image it is.
It will be hard work to find the image ...
I started with your first suggestion working backwards on the images most recently imported. I could see that this was going to take a whiile, so I switched to option 2, i.e., Update Preview." I didn't find any corrupt images in the those most recently imported, however, I remembered that I also noticed this problem ocurring when MobileMe albums were being synchronized, so I took a look at them. These images have been out there for a while, but I noticed a few that had a green tint to them and ragged colorful edges. It just seemed that something wasn't right about them, and they would change from this un-normal state to normal and back. I couldn't force a failure, but I was not comfortable with the state of these images, so I deleted them from MobileMe. I have quit Aperture and restarted it and up until now I have not encountered the original hang that was happening. I'll be more comfortable after a few days of use, but I am encouraged.
Thank you so much for your suggestions, Leonie.