did a little searching on the net and well it seems you are not alone
broken axle complaint
http://www.allworldauto.com/comments/viewthread.php?cid=618508
His dealer seems to have seen this before and another person also has had 2
http://www.carcomplaints.com/Ford/Windstar/2000/drivetrain/rear_axle_broke.shtml
I'll have to ask my cousin if his is holding up