Apple’s calendar software, iCal, has taken unfortunate steps backwards in Leopar, Mac OS X 10.5, which were not remedied by the 10.5.1 update.
When users of iCal under Mac OS X 10.4.x invite users of 10.5.x to an event, the behaviour is quite different than it used to be. Regardless of the calendar the sender had assigned an event to (e.g. Home, Work, etc.), when inviting a Leopard iCal user, the event arrives as part of the Home calendar.
Worse, it’s impossible to edit the event or its notification/reminder. You can’t change the Calendar to which it belongs, it will have a 15 minute alert — even when the sender chose an hour — and there’s no way to confirm or decline the invite.
Here’s hoping 10.5.2 addresses some of these issues.