What i see on your screenshot is:
1. Your deal is started on 15.04.2009
2. Your deal end WAS on 15.07.2009
3. On 15.07.2009 you made a rollover - this mean to continue your deal. When you made a rollover you told the system a new end date.
4. Now the end of your deal is 15.10.2009 - that's why you can post interests till 15.10.2009.
When i was trying to figure out the influence of Contract Close date - i haven't found anything.