Hello,
I've noticed that zero duration events are broken in version 7.0 of day pilot. I've rolled back to an old version of the DLL (version 6.6.2359.0) and the events are displaying properly.
For example: I have an event with the same start and end date (8/8/2012 10:00AM). I have the UseEventBoxes="ShortEventsOnly" property set.
In version 7, I tried changing the values for UseEventBoxes and did not see the event render at all. Version 6.6 worked well.
Possibly related, I've also noticed that zero duration events at midnight (12:00:00 AM) don't render in version 7, 6.6, or 6.4.