Bearing in mind that I know very little about Hibernate, I'd have to ask a couple of questions...
1. What was the value of "current_date"?
2. What were the start_date's the filter returned?
3. You do realize that that the number of days from 29/10/2006 to 03/11/2006 (assuming dd/mm/yyyy format here) is only 6 days, right?
4. Does current_date also contain the current time?
5. Does start_date also contain the current time?