The logic for closing a work order has changed with Build 35 - released on 6th March, 2012.
Previously, if any designated 'End' event for a work order had a date and it was the latest date in the list of events, the work order was deemed to be closed.
Now, all designated 'End' events for the work order must have a date or be marked 'NA' before the work order is marked as closed. The dates entered in the 'End' events need not be the latest in the sequence of events.
For any clarification or doubts, please contact firstname.lastname@example.org