When events are sent down from Davical, or when created originally by a device, there is no "Organizer" email set unless there are others invited to the event. Mobile devices will typically disallow editing unless you're the "owner", and they determine that from said field. There is a check for this condition in the existing code, but it sets it off this->originalUsername, which is not defined.
The following patch sets it to both the username and domain. Some phone devices (specifically, BlackBerry Android HUB users, although they're fixing this) demand both the user and domain or they won't authenticate, so we use both if the domain is also present in the common "@" (RFC822) format.