I've got an '04 and I am currently having issues with my 4x4 switch as well. If you do a search on the forum you will find that there are lots of post about faulty switches. With so many issues I'm amazed that there isn't a recall. Mine will go into 4Hi but not 4Lo. I have the extended warrenty but it cost me a $100 deductable so I am holding out to see if I can fix it my self first. Guess thats what Ford wants you to do
Anyway maybe we will get some answers. Good Luck!