Not able to send calendar invitations

The invitee gets it on their calendar, but not via email notification (so they have to look at every day of their calendar to see if something's been added tentatively). Likewise, I'm not able to receive invitations at all (on ipad or iphone, but yes, it's on the calendar - again, it's on my calendar if I know to look at it).

Apple tech couldn't figure it out either, so they've forwarded it to their engineers. This started with my business partners iphone, then it happened to his iPad. I tested the problem on my iPad (working perfectly with the calendar function) by adding his account, then it killed my iPad calendar invite function AND, then it happened on my iPhone.

In testing, I deleted my iCloud account (what I believe the problem is), and it totally deleted my ability to invite anyone from my Exchange (Google Apps for Business setup as an Exchange account) calendar screen (as in, it removed the "invite" option all together). This is the most bizarre behaviour I've ever seen.

So, when I go to my desktop, I'm able to send invitations just fine to other people that don't possess either my partners i-devices, or now mine.

Reminds me of the good old "Mobile Me" days...