One of our customers raised an issues with CalDAV accounts on an iPhone 4 (and possibly also iPhone 3GS). He indicates that when a new calendar is shared with the user (using the Zimbra webmail) the calendar does become visible on the iPhone, but it stays empty (it doesn't seem to synchronize).
He tested this and it turns out that when he uses 4.2.x it does work correctly, but when he uses 4.3.x this problem occurs.
At this time I don't have an iOS 4.3 capable iPhone at my disposal, so I am not able to replicate this at the moment.
Does anyone have any similar problems? By the way: our Zimbra version is 6.0.10