Just as we with the 03's are able to change CDs by holding the up/down button for 2 seconds, I understand the 04 owners are able to change "preset families" (as I call them) by holding the same button for 2 seconds. We 03 owners can only change to the next preset within the same preset family by tapping that button. We actually have to reach over and change preset families on the head unit.
If you have an 04, try holding the up/down steering wheel button for a few seconds to see if you can choose a different preset family (well, aux input in your case).
I just realized you may have actually meant that you can't even get into sat mode by the mode button in the first place. Is this what you are saying?