Outllook 2007 archive behaving badly

[Dan2]

I want to archive e-mails written before 31/12/06 from a specific folder, say F. That folder contains only e-mails written after 30/09/2006.

1. I select folder F and then File | Archive.
2. The Archive box pops up with folder F selected and "Archive items older than" set to Sat 30/09/2006
3. I set that field to Sun 31/12/2006 and click OK
4. I expect the files written between 30/09/2006 and 31/12/2006 to be archived. Not so, they still are in folder F.
5. I select again File | Archive.
6. The Archive box pops up with "Archive items older than" set back to Sat 30/09/2006. Apparently the modification of that date does not work.

Thank you very much for your suggestions.

Outlook 2007 SP1 on Vista Ultimate x64.