I have a user who when he tries to scroll down his email list, when he gets to the bottom and it loads more in that the focus jumps to the top email. So every time he starts scrolling down it jumps to the top and he has to scroll down the entire list again. It only does this when he has his reading pane turned off. When he turns it on, it works fine.
I did a search and couldn't find anything so sorry if I missed something.