iCal on 10.8.3: nested calendars do not show in list

I have just realized that I'm unable to create an event in a nested calendar (local On my Mac). If I attempt to change an existing event to a nested Calendar, I only see the top-level Calendar name grayed out (no drill down is possible). For example, if I edit the event, and try to change the Calendar, I am unable to select a nested calendar. The same is true if I rt-click an event and try to change the calendar.

Consider the following calendar grouping:

Calendar_A

Top_Calendar_Name

|----- Nested_Calendar_1

|----- Nested_Calendar_2

Calendar_B

I can create an event in "Calendar_A" or "Calendar_B", but not to "Nested_Calendar_1" or "Nested_Calendar_2". When the calendar list is displayed, it shows "Calendar_A", "Top_Calendar_Name", and "Calendar_B", where "Top_Calendar_Name" is grayed out (unselectable and not able to drill-down to "Nested_Calendar_1" or "Nested_Calendar_2".

Is anyone else seeing this problem?

The only workaround I have uncovered is to drag the event onto the nested calendar. I suspect this is a bug.