I just posted updated versions of my iPhoto AppleScripts which hopefully address many of the problems related to System Events errors.
As I was trying to nail down what caused System Events to throw occasional errors I found a bug which was my fault. If any other windows were open in iPhoto, (info, keywords, Keyword Assistant), iPhoto would sometimes throw an NSReceiver error. All extra windows will now be closed before setting any dates. Apologies for not catching that sooner or thinking to check whether other windows were open. Hopefully that oversight will account for the majority of NSReceiver errors.
All window references should now be numeric, even though I’m fairly sure the window is always called “iPhoto” despite the active user language. (I deduced that from running the application under a variety of languages while internationalizing the date handling, the window title was always “iPhoto” even if everything else was not English and using non-Roman characters.)
iPhoto is now more assertive about coming to front, this should make running from Script Editor easier since dialogs won’t be popping behind iPhoto.
Every System Events command is now wrapped in an try block and a loop. Errors will cause that function to be run again after restarting System Events. I did this in the functions to try and maintain portability, but it made the code much uglier.
iPhoto 5’s adjustment windows are wacky. They report themselves as “AXUnknown”, with a possibly English localized name “HUD”. These windows do not respond correctly to a close window command
iPhoto 4 and iPhoto 2 reversed the numeric index of the date and title fields in the info pane. I must the only person in the world who noticed that. If I remember correctly there was no iPhoto 3. iPhoto 2 is not currently supported, for whatever reason it wasn’t correctly incrementing selections via Apple Events. If it’s a quick fix, I might get that working at some point since I have access to a machine with that version.