I have a Xbox 360s 4GB currently with 2 4GB flash drives inserted. I just added a third flash drive (8GB) into the third port in the back of the unit. However, when I go to the Memory menu, only two drives plus the 360s memory unit show up. If I remove one of the three flash drives, the other two appear in the menu (so nothing's wrong with the new 8GB flash drive). Is there a problem with my 360s USB ports, or does the 360s only access 2 flash drives at a time?