I discovered why this is occuring. In my test event I set the Event Start Date to 9/26/2006, the Event End Date to 9/26/2007 and the Repeat Until Date to 9/26/2007. After looking through the code I realized the value for the Event End Date is the cause. The code that checks to see if an Event is occuring on a given day does not take into account if this is a recurring event it just does comparisons based on the Event Start Date and Event End Date, when I set the Event End Date to 9/26/2006 everything works fine. I still think this is a bug because the Repeat Until Date should always reflect the Event End Date, if nothing else that field should not be editable.