I was having a problem with AppleScripts which use UI Scripting in 10.4. Something was corruping the result of System Events’ UI Elements Enabled boolean, causing script execution errors whenever that item appeared in a script. Joe’s iPhoto AppleScripts use GUI scripting, so this bug stopped them from working. Deleting the preference file “com.apple.universalaccess.plist” and restarting fixed the problem for me.