Okay so I receive invites from my partner who uses Google calendar. I receive it at my iCloud.com email address (on both my Mac OSX 10.8.3 and iPhone 5). I know there's currently a bug in the Mac mail app when opening the attached invite.ics attachment it doesn't add the event to the default calendar I have set.... but that's another matter for Apple to fix. So I open the email on my iPhone and click the invite.ics attachment and that opens my calendar and asks if I want to Add to Calendar. After the event is added to the default calendar, I open the calendar app and select the added event (grayed out). At the bottom there are buttons for Maybe, Accept or Decline. Here's the problem - after I select Accept (or any of the choices) it never sends an email back to the originator so they know I have replied. On the Mac it does send a response. Is there something I am missing???