I expect that you have actually banked your December 2006 Use Year points - not your 2007 points. You are still in your 2006 Use Year until 12/1/07 when your 2007 Use Year begins. Since you do not yet have your 2007 points, they could not have been banked at this time.
The banked points from your 206 Use Year may be used to make a reservation between 12/1/07 and 11/30/08. If you wish to make a reservation for any date prior to 12/1/07 you would need to borrow your December, 2007 points since the 2006 points cannot be returned to their original Use Year.
As Jim pointed out, you should be certain to use your banked
2006 points first for reservations after 12/1/07 - since they cannot be banked again and will expire on 11/30/08.
With a December Use Year, you could not borrow from your 2008 Use Year for dates prior to 12/1/07 since points may only be borrowed from the following Use Year and you are still in your b[]2006[/b] Use Year now.
Use Year is probably the most confusing and most misunderstood single aspect for most members - especially those with a December Use Year. It's too easy to confuse Use Year with calendar year.
I hope this helps!