比較簡單又直接的修改方法，可以在以下 forum 找到：
節錄出來方便大家，和我自己（註 MM = MobileMe）：
When you change your MM password, you need to enter the new password in MobileMe in System Preferences. When you select MobileMe in System Preferences, it will (correctly) say that your password has changed and ask for the new one.
It looks like the problem with iPhoto is that when you enter the new password in MobileMe preferences, the keychain entry for it isn't being updated. Look for publish.me.com in Keychain Access. It will probably have the old password. Changing it there and then
注：我刪走「signing out/in in MM System Preferences」因為我發現無需要這樣做。我只是把 iPhoto 關了，再進行以上的修改，之後打開 iPhoto，一直就正常了。