Error -50 when using an external editor

Question

Having finally graduated from iPhoto 2, I found some "interesting" behavior in iPhoto '08...
iPhoto objected when I tried to save an externally edited photo back into its slot in iPhoto -- nothing lost, just an error dialog and the edits were not applied. Since it was repeatable, it made me curious.
When you choose external editor to edit a photo in iPhoto 8, the first thing iPhoto does is stash a copy of the original (and activates the "Revert to Original" menu item for that photo). Just editing in iPhoto 8 doesn't do any of this until you accept the changes -- that's an important distinction, because if you change your mind with the external editor (and make no edits, or cancel them without saving), that stashed copy stays in the "modified" folder.
For all practical purposes, it's "forgotten" unless you happen to choose "Revert to Original", in which case, the extra photo is unceremoniously purged. Now, if you don't think about purging that forgotten copy and later decide that you actually do want to edit that photo in an external editor after all, iPhoto will again stash a copy while your external editor is opening. It gets stashed in the same folder that already has the previously stashed (and forgotten) image file. If the file were overwritten, there would be no big problem, but it does not get overwritten, and you can't have two files with the same name in the same folder. So the finder appends a "_1" to the end of the file name -- and THAT sets up the problem. When you finish editing and save the file back to iPhoto, you will be (unintentionally) trying to add a file to your collection that iPhoto doesn't know about. The filename change to avoid a conflict in the folder is not reflected in the iPhoto 8 database.
Older iPhoto versions would have let that pass (and that's why there were always problems with database corruption), but the newer version catches the attempt and simply doesn't allow the save to take place.
That's the "why it happens", but it's only my second day with iPhoto '08 and I'll need a little more time to work out how to selectively fix the problem without damaging the database -- a database rebuild does not purge those stashed photos (and you wouldn't want it to because most of them are the originals for photos that were actually modified).

Answer 1

Brie Fly:
I tried to replicate that using Photoshop and could not. When starting an edit with PS a file is created and remains is I abort the edit in PS. However, if I edit again with PS and save the original modified file is changed with no other file being created.
What 3rd party editor are you using? The only time I get a _1 file is when I move a file to an event that has the same file name as a file already in that event.
What system are you running and are you at iPhoto 7.1.1, iLife Support 8.1.1 and Quicktime 7.3?
Happy Holidays
TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've created an Automator workflow application (requires Tiger), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. It's compatible with iPhoto 08 libraries and Leopard. iPhoto does not have to be closed to run the application, just idle. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.