Ever think you might want to trust your data to a giant?
It instills confidence when the "cancel" button is the way out of a "we were too lazy to "test and or implement" this bit.
Check this out:
http://social.technet.microsoft.com/wiki/contents/articles/17076.error-when-creating-a-new-shared-mailbox-in-exchange-2013-online-admin-module.aspx
Thanks Caroline Claeys, and Richard Mueller for documenting this for the beast!
Documentation posted by users for the product you are selling... Too funny.
Since they will just delete that later, here is the gist:
Error When Creating a New Shared Mailbox in Exchange 2013 Online Admin Module Situation Trying to create share mailboxes in Exchange 2013 Online Admin Center Full delegation and send as rights by one and the same person. I filled in the form to create a new shared mailbox. Problem After clicking 'Save', I received every time an error: error The items you're trying to open couldn't be found. Click here for help... If you click 'Save' again after closing the error message, you get yet another error message stating that the Windows Live ID is already in use. If you try to open the mailbox via OWA, you get another error message. Solution Cancel the input via button 'Cancel'. Refresh the list of shared mailboxes. Click on the newly created shared mailbox (it was created after all). Adapt the delegate rights (he 'forgot' the full access bit). Save Now you will have access to the mailbox without any problem. There may be a better way to do it, but I did not find anything. Until a little trial and error showed me a way. Hope this will save a lot of time for other people.