What image format is the file? I may be preaching to the choir but maybe some of this will be of interest to you?
Using Photoshop or Photoshop Elements as Your Editor of Choice in iPhoto.
1 - select Photoshop or Photoshop Elememts as your editor of choice in iPhoto's General Preference Section's under the "Edit photo:" menu.
2 - double click on the thumbnail in iPhoto to open it in Photoshop. When you're finished editing click on the Save button. If you immediately get the JPEG Options window make your selection (Baseline standard seems to be the most compatible jpeg format) and click on the OK button. Your done.
3 - however, if you get the navigation window
that indicates that PS wants to save it as a PS formatted file. You'll need to either select JPEG from the menu and save (top image) or click on the desktop in the Navigation window (bottom image) and save it to the desktop for importing as a new photo.
This method will let iPhoto know that the photo has been editied and will update the thumbnail file to reflect the edit..
NOTE: With Photoshop Elements the Saving File preferences should be configured as shown:
I also suggest the Maximize PSD File Compatabilty be set to Always. In PSE’s General preference pane set the Color Picker to Apple as shown:
Note: to switch between iPhoto and PS or PSE as the editor of choice Control (right)-click on the thumbnail and select either Edit in iPhoto or Edit in External Editor from the contextual menu. If you use iPhoto to edit more than PSE re-select iPhoto in the iPhoto General preference pane. Then iPhoto will be the default editor and you can use the contextual menu to select PSE for your editor when desired.
Give this a try: Try this: launch iPhoto with the Option key held down and create a new, test library. Import some photos, edit with CS5 and and check to see if the same problem persists.
Thanks for responding.
I did more tests and I think there is a code problem in the version of Iphoto 9.4.2 in how it interfaces with the external editor. In my case photoshop CS5. When the image file is returned to Iphoto it is not edatable with the Iphoto editor. I saved the same file from photoshop to the desk top and imported to Iphoto and it worked just fine.
Older images that were edited with PS with an older version of Iphoto worked just fine with iphoto 9.4.2.
I did this test with a new version of the Iphoto library.
I reported this as a bug to Apple.
If you try the same test and get the same results maybe you could report a bug also.