If I enter an event in to the Calendar with any Start Time, and choose "Without Duration" then no Start time is displayed in either the Calendar view or the Upcoming Events view. I updated to the latest version of moodle ('1.9.2+ (Build: 20080802)' for this testing.
I created 2 different events on August 1, 2008. 1 event with a duration of 60 minutes, starting at 8PM MDT (Test Event 1) and the second event (Test Event 2) starting at 8:30PM MDT Without Duration. Event 1 works just fine. Event 2 will display a start time. This particularly bothersome in cases where and event may start n the morning with no fixed time to end.