I think I've found a bug related with ReadOnly slots. Sometimes, double clicking on a "cell" inside a ReadOnlySlot causes the CreateAppointment or EditAppointment dialogs to be shown. It looks like ScheduleView is trying to edit the "current" appointment or to add a new Appointment on the "current" NonReadOnlySlot.
To check this issue, just go to Special Slots demo at http://demos.telerik.com/silverlight/#ScheduleView/SpecialSlots
and click on any empty cell of "Team Calendar" (ReadOnly Slot). You'll see that a new CreateAppointment dialog appears with start time: "07/02/ 2012 8:00", end time: "07/02/2012 9:15". If accept the dialog a new Appointment is created on "My Calendar".
Some times, after playing with the control (going forward or backward) the problems seems solved and the control doesn't longer allow to "add" or "edit" appointments on ReadOnly Slots.
This is a really annoying behavior for me as I cancel all ScheduleView dialogs and create new appointments "silently" each time a user double clicks on an "allowed" cell (a cell not inside a read only slot). In my application I've seen that, depending on the present appointments, clicking for example on a readonly cell a new appointment is created a few months ago or later (I supose it dependes on the "selected" appointment in ScheduleView).