You have heard my tales of woe about not being able to use my LDD3 yet, so I am no expert on the newer AutoCAD by any means. BUT, what happens when you go to "DIMSTYLE" , to the style manager, select the "text" tab, go down to the "Text Placement" block, and set the vertical window to "above"?? That sounds too simple to work though.
Never mind. I just tried that and it didn't work. The only way I have found to do it so far is to set the leader and text at 0 degrees and then rotate them both 90 degrees. Not a good answer. Give Keith a minute and he will have you a lisp thingie.